I've been using steroids off an on since '95. Back when I was having fertility issues trying to knock up the wifey the endocrinologist said lay off the gear for a full year and see what happens. Well after a year I managed to knock up the wifey. I stayed off for a while after that, I actually learned to enjoy natural training, since I was paying so close attention to my diet I was pretty lean, also I ventured out trying different sports with some friends. Anyways to make a long story short when I went back on I decided to do 6 weeks on with 8-12 weeks off and made some incredible gains. Looking back I can see how you can build up a tolerance to steroids and after a while 1000mg-1500mg of test per week isn't packing the bang it use to have. Now I'm not saying Jay Culter is running 6on/12off of course and running 1.5g test/wk works better.
With that said a definitely downside to 6on/12off was the ups and downs of steroids becomes apparent. Your first 6 week you might recover natural test but after a while recovery is slow. Where as I think staying on a lower dose for longer is probably safer and less ups/downs which is what a amateur non-competitive guy is probably looking for.