I used to be able to self-suck. I was probably 15-16-17 during the years when I actually put some effort forth at autofellatio. It was fun to be able to say I could, but I didn't have all that much fun because it was actually pretty uncomfortable. (I'm currently 7 7/8 with a really good boner and the ruler pushing against the pubic bone, and I was probably not much shorter back then.) If I was bigger I might still be able to do it today, and I might truly enjoy it; back then, I had not yet had experiences with a woman, so I was not completely familiar with the pleasantness of having my cock sucked.
If I start some good (fitness/body) stretching routines, and lose, say, 25 pounds, I might be able to do it again while I'm still young. (I'm 31.8 years young.)