I bought my 2001 GS new in 2002. It's been a reliable bike. Only twice - 1: low battery, 2: flat tire - did it ever prevent me from going anywhere. The first few years I rode only about 5,000 miles/year. It has over 48,000 miles now - two XC trips put more than 20,000 miles on the bike. I have adjusted the valves, changed the oil & filter, and replaced an alternator belt (preventive measure) in campgrounds. That's no big deal. The tools are basic and simple. The access to the engine is almost unlimited.
Besides tires and brake pads, oil, filters, and clutch/brake fluid changes (all normal & easy maintenance), I have replaced the shocks with Wilbers, replaced the brake lines with braided lines and I recently removed the charcoal cannister (in the way of some new side Hepco & Becker side case racks). There are plenty of farkles, but they are personal preference items. None were really necessary and none have failed.
It runs, rides and looks great. It's been inexpensive to operate - I do all my own maintenance work and I know it's been done right, so I ride without worries.