For most artists, hotttnesss and familiarity will update on a daily basis. For long tail artists, the update rate will be less frequent, but those are most likely to be artists that you don't care too much about.
Thanks for pointing this out. A grammy win might not translate into a huge hotness increase right away. I just verified that Sam Smith and Beck have had their hotness values updated on a regular schedule the last few days. It seems they've seen a nominal bump since Sunday.