A lot of compounds if not all .....require deep intermuscluar injection and unless you are lean or even completion lean then I would think twice about using a slin pin as you always want to ensure that the compound is injected deep enough without the risk of the oil or water carrier laying on top of the muscle rather than in the belly...
If you rotate sites constantly then you should last a while before you start to build up scar tissue which will mean no real need for slin pins

Used insulin pins for test e? Yes, all the time for many compounds. im lean enough to where I can use a 1/2 inch slin pin on my quads, delts bis tris. Just not glutes. This all has to do with how lean the muscle group is, jusr because I can doesn't mean you can. But you might you just can't have much of any fat covering the muscle or you'll end up with an infection, absess etc. You have to backload the slinpin, since most don't have detachable needles it's not sterile to draw with the same needle you pin with not to mention it will be dull after puncturing the vial.