Anuj... you make me sound like superman!
Truth of the matter is that my 20 rep is not even close to 400, though I may be looking at 300 by the end of this year. I have backed away from training them but once a month, and I've aimed at doing a percentage of my current working max, not making the 20 reps a max in itself.
I'll probably hit up 20 reps every week starting this winter again. Since I work out in the garage (temp = 2.5 degrees warmer than outside if I'm lucky) I try to keep my work brief and highly taxing. 20 reppers are great for this, though I have noted a small decrease in my actual 1RM, though I suspect this is only a very temporary thing, and I expect to crush my old max in short order (maybe a couple months).