The rewards for any endeavor are internal. You just shouldn't put too much stock into external shit. We all get older and you don't want to be one of those guys on here talking about how they looked 30 years ago or continually adding drugs.
I know what I want and what I "should", I wish the same for you. And no, I def don't want to be one of these guys. I want to keep myself in a peak shape for as long as it is physically/genetically possible for me and I am ready to go great lengths to achieve that, it's an exciting and scietifically arousing feat by itself for me, it is more about the journey, as Kane SUmabat says - it's not means to and end, its an END by itself.
I feel like most people doesn't even have a direction and are slowly waiting for death after age 50 anyway, so I should be allright. At the worst case I'll loose all my muscle, but at least I know that I've tried, while most are lazy, lifeless and scared to attempt anything in life, to dream big, even if it's futile (and it is futile - we will all die at the end).