from the time you start.. till when your done ...

why look at the clock ?

im usually at the gym for 1hr 45 mins

It just depends on ur rest times and what your goals are if you want get strong of course it's going to take a couple hrs bc u wait 5 min between sets but if u do 60sec between each set u should be able to knock it out in 1 hr or less unless people talk to you all the time which is what I hate lol

Until I can barley lift anything than Im done

On-cycle I'm in the gym 7 days week for at least 1.5 hours and up to 2 hours. Off cycle I try to keep it to an hour or less 4-5 days/wk. Main reason it takes longer when on cycle is because I now work 2 body parts per day (except for leg day).
The key is to listen to your body. If you can't give it 100% towards the end of your workout it is time to stop because you will be shortchanging that bodypart by not being able to fully work it to its max.

Yeah i think best way is just listen to your body.have your plan but if you feel strong do an exercise/ intense set more etc and if you feel weak just go in there do one heavy shit 5x5 or something and go home afterwards. It doesn't really help anything if you are tired and try to do your 90min high volume workout

When I was young I worked out 2 hours or so a day, had great results, minimum supplements too. Then I started reading more, my form wasn't the best, etc. Read how many sets what I should do how to do it etc etc etc results were average at best
now Im back into listening to my own body, sometimes I hit the sane muscle groups 2 times HEAVY a week. you can't base strength or endurance off of an article