That's an interesting question actually, when you introduce raising blinds soon. The major function of M or x big blinds is not really to see how long you have left, it's basically for size of pot compared to stack and when you can push. If you are 100 BBs deep (no antes), even if next hand the blinds will be half your stack, I still think it would be a mistake to shove 78s from MP. If the blinds were 1/4 of my stack (ie 4 BBs) and next hand they go up to 1/2, I shove 78s from MP all day just because I'm getting such great odds
on the shove.