I usually get away with never having to rebuild them. In summer you're fine but in winter it's ESSENTIAL to wash the calipers down after every ride.
I've got my hosepipe wall mounted just inside the garage door, when I get home I spray the living daylights out of all three calipers - really hammer them from all angles. Then shove the bike in the garage until next time.
Works a treat.
If you do need to rebuild, make sure to scrape the seal grooves spotless with a right angled pick, get all the chod out or they'll just start sticking again.

**EDIT** should have watched that video before posting. 

I went +1 on the front.
It takes less than a 1/4 hour (assuming you've got an air impact wrench) and has knocked about 7-800 RPM off in top gear.
I haven't noticed any difference in acceleration, bloody fast is bloody fast if you ask me.
It's a lot more relaxed now and 7K RPM cruising at 90(ish) is fine for the big miles.
IIRC it's doing about 4.5K RPM at 60MPH, it still picks up from there but a change down to 5th is needed for a quick squirt round the cars.
One thing though, it struggles to rev out in top, it gets to about 125 and runs out of puff so for top speed runs it's a case of 5th and scream it.

***All speed tests were done on private roads****

They are pretty crap at repairing roads it's true (Sheffield).
This was taken on Houndkirk Moor, all the locals just call it the Roman Road.
I've been exploring a few more in the Peaks, it's pretty good at it - I avoid the steeper muddy ones, but that's more to do with the tyres on the bike, rather than the bike itself.
It's really good in sand, I always hated sand on my enduro bike but the wide front tyre seems to flatten out the ruts rather than following them and pitching me off.
The only thing it definatley doesn't do is drop offs, but the exhaust makes a pretty good bash plate!