It occurs to me to write this, as it's happened now a few times.
Car runs well for quite a while, then... dum-dum-dummmmm, things get dark and scary.

Well it doesn't run so well. Slightly high idle sometimes, slight catch on take-off, tiny bit less power maybe (bad gas?) just... different things. Then the other day it quit while driving, for about 2 seconds. Just long enough to have me think over where to pull over. In a tunnel. With no breakdown lane.

So in an attempt to do one thing at a time instead of firing the parts cannon, I pulled off the power stage, cleaned the old paste, put on new, and replaced. Startup was at least as good, running was smoother, power was back, all issues gone, runs great.
The paste does get hard over time, so... Radio Shack has small tubes for about $3.