do you have to be on it for life? i feel like i'd only wanna go on for a period of time, to avoid major hair growth and hair loss etc?
If you want your change to be consistent, then yes. If hair loss runs in your family and it concerns you, try asking your doctor if there's anything they can do for you to help ease that. They should be able to give you some advice
If you stay on it for a while, you'll get changes, and then some will reverse, others will stay. You'll keep any facial hair you get, your voice will stay deep, and if you're of an age to grow a bit (lots of people I know have grown a tiny bit) then you'll keep that. Body hair decrease, and go back to how it was before within about a year, and muscle mass, metabolic changes will reverse etc. It's a thing that people do, though in my experience it's more common in non-binary people who don't want all of the changes.
There are options to reverse the "irreversible" changes, but they're pretty much the same as for transgender women. Laser/electrolysis to remove the unwanted hair, glottoplasty for voice. The only one that's truely irreversible is the clitoral growth, but then that's the goal of many who don't plan to stay on testosterone for a long time.
If you stay on T for a short enough period of time to avoid significant hair growth, you're also going to miss out on some of the changes you probably want (e.g. your voice won't drop all the way). Going off before you start losing hair is more feasible, depending on your age. Some effects will reverse when you stop taking T. For example, you will revert to typical female fat distribution patterns, and it will no longer be as easy to gain muscle mass (you will probably lose muscle mass when you go off T). Clitoral growth, hair growth, and lowered voice are the main permanent effects.
