I have also fired a lot of rifle rounds with part of the bullet intruding into the powder space. No problems have arisen so far, either functionally or accuracy-wise, even in rounds loaded many months prior to firing.

HOWEVER:

-If the ammunition will be exposed to very hot conditions, there's a possibility that melting lubricant can contaminate the powder, or even the primer (a more remote possibility).

-Most of my cast-bullet rifle loads use a loose dacron filler, which positively prevents the powder from contacting the bullet.

-Some of my cast-bullet HANDGUN ammunition, in conventional straight-case calibers without any filler, and thus with the powder in contact with the bullets, has survived several years of storage in a HOT shed in desert temperatures (likely over 130 degrees), and then performed in a totally-normal fashion. I take care to ensure that bullet bases are CLEAN when loading, but that's all. Obviously the lube doesn't migrate between case and bullet even when liquified.

I'd say not to worry about your bullets extending into the powder space, UNLESS hot temperatures are expected. In that case, you should be careful to not allow the ammunition to reach temps that could melt the lubricant. Maybe do a test with a sample of your lube to actually see just where it starts to melt? A cooking thermometer, some lube, and an old pot might teach us something....I might just try this myself!