I used Moori Med's for years & have recently switched to Everest. I don't have much - maybe 15% - taken off at install, the Everest seem to play well right away like that for me. The layered tips are harder the further down you start, so you have the chance to personalize them a bit - or ruin them for yourself if you start to low for your liking.
As for replacement, I think each tip has it's own "personality". Some require more frequent roughing to break the glue transitions, some just get firmer faster, etc. I go entirely on feel for replacement, but I do try to play a pair of shafts in at roughly the same rate for consistency. Then I'll replace one shortly before the other to allow for some turn over time. Generally, it doesn't entail much lost motion because I tend to get used to the tip being harder at the end of its life (for me) and get a bit dissatisfied. When I get the new tips on, it feels like more of an improvement than a hinderance.
One other thing - with the Mooris... Something I did w/ them that I learned from Alan McCarty... I'd have them installed & domed, then I'd take them home, put the shaft on my cue, and drop the tip onto a hard surface about 100 times from a height of about 18" or so. Kinda gives the tip a little "tempering". Then when you re-shape it, it'll hold up very well.