I've been playing for 5 years, but only started to sweep when I "discovered" COB. Personally I think it doesn't matter wether you start with 3 or any other number of string sweeps.The important thing is that you practice it slowly the first time(no-one likes sloppy guitar playing) and build op your speed over time.
Try understanding the theory behind arpeggio's too, so that you can write your own arpeggio's, it would also make it a bit easier to remember some sweeping pieces.
Another excellent example of sweeping to begin with is Silent Night, Bodom Night.
Just don't go anywhere near Kissing the Shadows!