Without actually measuring these numbers, I'll guess an alto reed takes several (couple hrs?) hours to break-in, and probably good for at least 20 continuous hrs, many times quite a bit longer. And that's blow time, not holding/reading time. Also, the loss in performance is not that drastic, and you can play them even longer, although you loose volume, add squeeks, register change issues, they overblow much more easily, etc. You have to be on guard of damaging one from chips and splits. Even more likely than that, is warping one by improper handling and drying after play, by leaving on the mouthpiece or other issues, like residue buildup on the table.
You can read and learn how to extend reed life. I don't look at it as extending life, as much as keeping the reed in top performing condition, like a vehicle, or a kitchen knife. Removal and proper storage is important. Rotating reeds is good, I only rotate two, and use my primary till its time to replace it with the backup. That's just me. And when its time, clipping the tip, and leveling the underside with a scraper or razor blade extend life. When I was gigging, and I'm not gentle on reeds, I really think the cycling was more influential, as if the wetting/drying cycle influenced reed life a lot more than blow time.
A new, broken in, adjusted* reed is a wonderful reward. And it always reminds me I'm stingy about hanging on to reeds too long.