I don't have any form of routine, really, and I'm pretty lazy when it comes to using the practice pad.
To work on rudiments, I'll occasionally sit down with the pad, but otherwise, it all gets practiced on the kit, in beats, in fills, etc.
I find I learn rudiments or stickings easier if I play songs that involve them, Whether I can play them correctly or not is another story; I just play until I can replicate the correct sticking. I'll usually focus on said specific rudiment for a while, messing around with it, before adding it to my 'repertoire'.
Sometimes I'll sit down and just play variations of the same thing over and over and over, until it drives everybody in the house crazy. Like when I was learning the 2-over-2 triplet fill, I just did it over and over, until I was able to play it cleanly and with speed.
As for deciding to learn new things?
I'll learn some new rudiment if I feel it will benefit the music that I play in some way. I primarily play for fun, so frankly, I don't care if I can't play ratamacues, inverse paraddidles, 9-stroke rolls, etc. Unless of course I hear some awesome fill or groove, and just HAVE to learn it, I'm very happy with where I am, skill-wise.
All that to say I'm lazy!