I've got 2500 to 3000 miles on my Y2K 520 EX/C with no problems. Oil changes, valve adjustments, chains, tires, wheel bearings - all the usual stuff. My bike was also Dual Sported day one but most of the miles are HARD, ROCKY Pennsylvania trails. ( I wore out a carbon fiber bash plate within the first year- thanks to all the big PA rocks).
I keep my bike in good mechanical condition. That cost money. Got to PAY to PLAY as they say. If your getting a good price on the bike then don't worry about it. Get it, RIDE it, and go over it BEFORE time and money allows. If you wait till it's broke it's too late.
I thrash by bike pretty hard. Can't believe nothing broke. Bent a few things, and a few things fell off. Melted a thing or two, but NOTHING broke.
Get the 520 - YOU WILL LOVE IT.