Well I just re-tested my MSI 4070 Super Gaming X Slim. I got it back in January, and I reckon ambient temperatures were 3-4°c lower then.
Running the same tests, GPU temperature max was 4.9°c higher, hot spot was 8.1°c higher. Not much of an increase when normalised for ambient, but still an increase. Funnily enough the memory was exactly the same as before, and that uses pads, which does point to the paste getting less efficient, rather than dust (of which there is some).
Disappointing, but not all that dramatic. Don’t think I’ll need to repaste any time soon.