I have seen several fermentation schedules that call for the fermentation temperature to be raised progressively over the coarse of a few days. I have seen this type of fermentation in both lagers and ales. What does this type of schedule do? What’s it’s purpose?
For the most part it's something that has just become homebrewer standard practice for many. The idea being to keep the yeast warm, happy, active and keep them working after the bulk of primary fermentation. It is "claimed" it can help a beer attenuate better, keep from stalling out and some will say give the beer time and a better chance to "clean up after themselves".
What I do and I would think most others do is I don't have detailed or exact fermentation schedule. For the first 3-4 days or so of fermentation I will control my temps, after that I will just let temps rise from there within reason. I don't get particular about going 1 degree per day or ferment x days at 65, then 67, then 70...etc. Control primary fermentation, but after that I rather let temps rise a bit then fall. I do not brew a lot of Lagers, but the same idea applies. For Ales and Lagers especially, a D-rest at a warmer temperature is often suggested. But starting with a good healthy yeast pitch and a good fermentation, these extra steps aren't really necessary IMO but the idea is...well it doesn't hurt either.