I know lots of guys who never come off... their health is fine.
It's the asymptomatic health affects that you need to worry about. Until you prostate swells up to the size of a grapefruit, you may seem perfectly fine on the surface. Permanent damage to your body's endocrine system may not be detected until you've long passed the point of no return - I know this is debatable, but I wouldn't want to spend countless hours visiting endocrinologists and trying different hormonal concoctions just to return my hormones to normal levels.
Trust me, I'm sure anyone who's stuck a needle in their ass has probably put some serious and in depth consideration for this. I'm damn near willing to take the bullet, but I'd like to wait until I'm a little older. I'll definitely be on a good TRT program when I'm around 40, whether it's self administered or legally prescribed. It's just a matter of should I mess myself now, or later when I'll be on the decline anyway.
