I could see waiting longer than annually without much issue. My high pressure pump time is probably only 2 minutes per wash and at 10K washes that works out to 333 hours. I could probably move that to every three years without worry, but every spring I change out a lot of unnecessary stuff in the SS to keep the place looking good so it's easy to just do it then.
On the other hand, I think I've changed the oil in my 3535 once in twenty years
Also, I don't bother changing nozzles on the cloth wash, because I'm less worried about spray pattern wear as their job is to mainly rinse.
Nozzles have gone up quite a bit, they used to be about $3 each just a few years ago. so it wasn't a big deal to change 18 on the water wizard. They are now a little over $5 each.