Thomas Shey
Legend
There's a balance to strike. If the rules change constantly, or even just too often, you're not really playing a game anymore, you're in Eternal Beta Test, which suuuuuuucks as a player. If the rules are utterly inflexible and never adapt to anything ever for any reason, that too leads to problems.
Another way of saying this is that your "If needed" is doing some incredibly heavy lifting there. If that happened more than, say, once every several months (of weekly sessions), I'd get pretty annoyed as a player that the rules weren't being consistently applied. If it happened quite regularly, e.g. multiple times a month for weekly sessions, I would be looking for a chance to have a heart to heart with the DM.
Fixing a real issue as soon as possible is a good thing. Preserving consistency and reliability is also a good thing. We must balance the needs of those two things against each other. I very much doubt there is one universal midpoint, but that midpoint shouldn't be abruptly changing all the time.
I think it also depends on how much a group is shaving a system down to their needs. Not all games come out of the can well suited to a given group (or even, honestly, as well designed as they could be). Ideally you figure this out before hand so you can work out houserules with people before you even get into it as needed, but there are always those things that look different on paper than they play out.
Some of it can, of course, also turn on how fussy you (as in both individually and a group) are, too; the degree of house ruling I bother with now compared to what I'd do in my 20's and early 30's is considerably different (of course it doesn't hurt I'm better at assessing a system by reading that I was back then, too).