I'm not really sure that there's an easily describable way to decide how far back to go with resharpening. It's a bit like describing how to fry an egg to someone who's never cooked. Once you've fried a couple of eggs, you just know when things are right.
It probably depends a bit on what tool you're talking about, and what work it's doing. A finish carving chisel or fine paring chisel will start to lose it's razor sharpness quite soon, but a lick or two on the polishing stone and it's OK again. When the lick or two on the polishing stone doesn't restore the edge, it's time to hone again, then repolish and off you go again. With something like a jack plane iron, once it starts to feel that it isn't cutting well, it's probably best to start right back with a coarse grit, though you won't need to go all the way to fine polishing to get it cutting sweetly enough again - it's doing coarser work, after all. A smoothing plane on final finishing work might need regular touching-up on the fine polishing stone, but for general fitting and clean-up work leave it longer, then hone and polish when it starts to lose it's 'bite'.
The best bet is probably not to worry too much about it, just dive in and do what you think seems right. After a while, you'll suddenly realise that it's become second nature; you just do the minimum sharpening to get the work done to the right standard, pretty much without thinking about it. You'll probably find after a while that you effectively ditch all but two, or at most three, grits - a coarse honing grit, a final polishing grit, and maybe one intermediate. I just use two - honing and polishing. If honing takes too long (more than about thirty seconds to a minute), it goes back to the grinder and another cycle starts.
