Similarly with my Model C, chain oiling (I still have some clear oil in an original bottle, so not that often), seat rollers replaced as bearings not sold separately (clacking noise like Oranj's - they looked fine but the noise drove me mad), regular roller & track wiping, fan housing hoovering, occasional grip scrubbing.
Every part available, and exploded diagrams & instructions on the web. Properly rebuildable; non-metric (US) fastenings are a bit of a pain, though. If I bought one now, I would want a dynamic one (or a Rowperfect) to get nearer to on-water feel, actions & timing.
Whenever I see a WaterRower I keep thinking of Legionella...