I always keep up with all techs but I try to never pay the ahead of time penalty. So that means investing in ideas with the excess. Unless there are particular ideas that are definite positives over the tech.
There are certain tech levels that don't give much of anything, so it's sort of relative. But each case is unique.
Sometimes, I find myself still with excess points, then, I'll spam buildings to use up the points. Buildings like Armoury, and Temple, I usually have in every province.
It would be different depending on whether you are playing as a western tech or not. Western can't save over 999 points. If as a different tech group you may want to bank points for certain reasons, the entire strategy could change.
I don't like falling behind in MIL tech because of combat repercussions.
I don't like falling behind in Admin tech because of the idea slots it opens.