I usually get around 6-8 days' worth, and sometimes 10, from both AC and injector SE blades, but that depends on the blades. I suppose I could push it a bit further, but it hardly seems worthwhile when a new blade is so much more pleasant to use. It is my experience that Day 1 of either blade type isn't the best, but subsequent days are fine until the performance drops off as the edge wears off or clags up.
I bin a DE blade after 3 days; no exceptions. On that turnover, I could expect to get 3 days worth out of each halved, less expensive DE blade i.e. 6 days all told per blade. Of course, DE blades in DE razors are usually and randomly alternated edgewise every time they're used, which spreads the wear, but, in practice, I find that a good quality half-blade in the Focus goes 3 days. The same for the Rocnel, unless it bites me, which it has a habit of doing with the corners, and then it's immediately sent back to the doghouse.