[once_inc]

Expected time to first block confirmation is always 10 minutes. If the last block was found 10 minutes ago, then the expected time to the next block is still 10 minutes. It is always 10 minutes until it is actually found, at which point it is still 10 minutes.

The only thing that can change value is if the global hash rate significantly changes. This is why we have the difficulty readjustment every 2016 blocks (give or take 2 weeks).

[olalonde]

Oops, you're right, I forgot about that. Updated my comment.

https://bitcoin.stackexchange.com/a/3911