I am 33 years old now and I started using AS after about 10 years of natural training. Therefore I had a really solid base of muscle prior to my AS usage.
For the first three years of my AS use I stayed on 365 days a year. I didn't want to come off because the transformation I was seeing was amazing. I didn't realize the difference between "natural" and "enhanced" until I became "enhanced". Then I started thinking smart (about my future health), and began cycling between on and off.
I spent the next few years with 6 months on and 6 months off. Always using extensive PCT. This gave me solid gains and the mental confidence that I was not damaging my body.
When I hit 30 years old everything changed. The PCT was not as useful in getting my natural test back, and I suffered by losing gains I had made while on. This takes an emotional toll - I hate losing gains!
So, now I do 9 months on and 3 months off. I'm ready to be off for December, January, and February. Will use HCG, Nolva, and Clomid (plus Cialis) and keep my fingers crossed that I don't shrink up too badly.
It sucks getting old!
BUT - here's the key... For most of us this is nothing more than a mental thing. As my wife points out, even when I'm off I am still bigger than 95 % of all the jokers we see in the gym every day. So I may not be as "freakishly big" as I want to be, but I have to learn that just being "big" is good enough for a few months if it means living longer and happier...
Sorry for the long post