Alcantara is an awkward material, goes with the territory of a "man made" suade, not a lot you can do with it!
I think its best to just keep it clean, as the dirt can work its way through the material, and that's when you can start getting cracks etc
As with most things, AutoGlym is probably a good place to start, i'm sure they do some shampooo and cleaning gear that you can use on Alcantara... possibly even something to protect it etc...