You can run it as long as you want but you are putting your body through more oxidative stress as well as a neurotoxic, nephrotoxic, and cardiotoxic environment.

I mean, probably the less time on the better, I wouldn’t really try and see how long you can run it

I’m 4 weeks in and oddly all my lab work actually improved??

You can technically run anything however you want as long as you want.

Brother, your protocol discipline is genuinely good daily pins, monthly bloods, locked diet, fasted cardio, BP at 112/61. You're doing this more carefully than 90% of guys. But your core question contains an assumption that's worth examining, because it's the assumption that gets careful guys into trouble: "if my bloodwork stays stable, I can keep running it."
The problem is that tren's most serious risks don't show up on standard bloodwork. Your panel isn't measuring the things tren actually damages over time. So "bloods are stable" isn't the all-clear it feels like you're monitoring the wrong instruments for this specific compound.
What your monthly bloods DO catch: lipids, liver enzymes, kidney markers, hematocrit, glucose, hormones. Real and worth tracking. Tren can affect some of these (lipids, hematocrit) and yours are holding, which is good.
What your bloods DON'T catch, that tren specifically damages:
Cardiac structural changes. Tren drives left ventricular hypertrophy and cardiac fibrosis through mechanisms independent of BP and lipids. Your heart muscle can be thickening and developing fibrotic tissue while every number on your panel stays perfect. The only things that catch this are an echocardiogram (for LVH and function) and cardiac MRI (for fibrosis). Standard bloods show nothing. This is the big one guys with "perfect bloods" on long tren runs who develop cardiomyopathy didn't see it coming because they were watching the wrong gauge.
Cardiac electrical/autonomic changes. Tren affects heart rate variability and autonomic function. Not on a blood panel.
Progressive neural/cognitive effects. The animal data on tren and neurodegeneration (β-amyloid accumulation) is concerning and wouldn't show on any bloodwork. We don't have human data, but "we can't measure it" isn't "it's not happening."
Coronary plaque progression. Even with stable lipids, androgens accelerate atherosclerotic progression through mechanisms beyond the lipid panel. A CAC scan or CT angiogram measures this; your bloods don't.
Kidney structural changes. Tren is among the more nephrotoxic compounds. Creatinine and eGFR are lagging indicators significant kidney stress can be occurring before these markers move, especially in someone muscular where creatinine is already confounded by muscle mass.
The core issue with your reasoning:
You're treating stable bloodwork as evidence of safety. But bloodwork stability over 10 weeks tells you that the markers bloodwork measures are stable. It tells you nothing about the cumulative cardiac, vascular, and neural changes that tren drives silently. Those accumulate with total exposure (dose × duration) regardless of what your panel shows.
It's like checking your car's fuel gauge to assess whether the engine is wearing out. The fuel gauge is accurate and useful for fuel. It's just not measuring the thing you actually need to know about.
The "barely changed from cruising" observation:
This is actually a slightly concerning interpretation, not a reassuring one. 200mg tren ace on top of your cruise should produce SOME measurable shifts (lipids especially tren is hard on HDL). If your markers barely moved, possibilities are: you're an unusually good responder (possible), the timing of your bloods relative to pins is masking changes (possible), or the markers that matter for tren just aren't the ones moving. None of those mean "tren isn't affecting me" they mean "the visible markers aren't showing it," which loops back to the core problem.
The honest answer to "how long can I run it":
There's no bloodwork-based answer because bloodwork isn't the limiting factor. The limiting factor is cumulative exposure to the silent damage. The honest framing from the actual risk literature:
Tren is best used in defined, time-limited blocks (8-12 weeks), not run continuously
The cardiac and neural risks scale with total lifetime exposure, not with whether any individual panel looks good
"Year-round tren" is one of the genuinely worst patterns in the entire AAS space precisely because guys feel fine and their bloods look okay while damage accumulates invisibly
200mg/week isn't a low dose it's a standard moderate tren dose, enough to drive the silent effects
What would actually tell you something:
If you want monitoring that matches the actual risks rather than just the convenient ones:
Echocardiogram at baseline and periodically (LVH, ejection fraction, diastolic function)
Consider a CAC scan to establish coronary calcium baseline
Track resting heart rate and HRV trends (your watch does this) autonomic changes show here before bloodwork
Take the night sweats seriously as a signal that tren is systemically active, not as a minor annoyance
If your echo is clean and stays clean, that's far more reassuring than stable bloods. If you've never had an echo, you don't actually know your cardiac status regardless of how good your panel looks.
Bottom line:
Your discipline is real and I don't want to dismiss it. But you're asking "how long can I run tren if the gauge stays green" when tren's dangerous effects don't register on that gauge. The answer isn't a number of weeks it's that continuous tren is the wrong framework. Run it in defined blocks, get cardiac imaging if you're going to keep using it seriously, and don't let stable bloodwork talk you into "indefinitely" because the bloodwork was never measuring the thing that matters most for this compound.
Feeling great and having clean bloods on tren is exactly the situation where guys run it too long, because nothing tells them to stop until something already went wrong

blood work isnt always telling the whole story. but anyway, your lipids are still in range after 12 weeks? 200mg is a lower dose so its not as bad as higher doses, but if i were you i would NOT go past 20 weeks but thats a high number that alot will disagree with. most are gonna say 16 week max. but people are pushing things to the extreme now so the old gidelines go out the window nowadays. but honestly, your body is probably gonna start to get used to it soon and the results will probably peak soon, then its just gonna start to affect appetite and you are gonna be burning more calories than you are able to put in and its usually not beneficial at that point. but everybodys body is different and goals are diff. i ran it for 16 weeks and towards the end it was a waste, i couldnt eat and felt like trash. wont do it again. probably wont ever take it at all again.

Do you just ask for advice and then neg the answers you don't like? Nice approach.