IS a next 50 an option to Advanced Search anytime soon?
Definitely. I have a project to take care of on SI that'll take a few days, then I'll come back here and do that.
It likely won't, however, span the year gaps. If you've Previous-50'd your way back to the beginning of 2005, it probably won't jump into 2004. I won't know for sure until I can focus my attention on it and see if I can make that possible without too much work for me or the machines.
It'd be pretty cute, though, to do it that way.