How long? 1 round.
As noted, the trigger smooths out after a few hundred rounds; it's a good reason to dry fire it.
I used to detail-strip and clean my XDs fairly regularly, just because it made me feel better, but it is somewhat time consuming to do that in addition to the cleaning. Maybe an hour the way I do it.
More recently, I've taken to spraying out the lower with Breakfree Powder Blast, which flushes the junk out of the lower quite effectively. Once it dries (maybe 10 minutes if you shake the pistol a few times), I follow with a few squirts of Breakfree CLP to coat all the metal parts.
With the slide I simply clean it as best I can without stripping it, though once in a while I will take it down all the way and clean it. You can Powder Blast that as well, but you have to be cognizant of the fact that you'll get this stuff into the striker channel, and it won't dry out readily. You don't want a lot of crap in the striker channel anyway as it will eventually gunk things up and may result in light primer strikes.
PS: I talked to Springfield Armory about using Powder Blast on the polymer and they said it's fine. And my experience is that it is.