The biggest things to achieve the ultimate in machine life are:
1) don't crash the machine! into things, into itself, into anything.
2) don't over-stress the machine: use reasonable feeds and speeds, check and double-check them, and somehow manage to never make a mistake.
3) Workholding clamps and fixtures are important to get right...and not run into!
4) Keep the static down to prevent controller failures.
Then there are exotic things like
5) Don't ever run the machine
6) Only "cut air"
7) Work only in EPS...or "expanded polystyrene", aka styrofoam
Anyway, apologies if I spoiled the serious nature with those last few

.
In and of itself, cleaning the dust off and lightly lubricating the slides and leadscrews, is all the active maintenance you should need to do. The steppers don't need lubrication. You'll probably want to add checking the screws attaching the stepper motors to the lead-screws, but only as a precaution; some have had their's loosen.
You'll eventually need to replace the router motor/bearings/brushes or the spindle motor/bearings. That's probably the one long-term "wear" component, if there is one. I've heard of routers dying in mere months, while my spindle (used for some pretty-heavy aluminum milling) is doing just fine after 2.5 years now, and I've heard of spindles being Dead On Arrival, and people who say their router has lasted years. YMMV is I suppose the rule here.
Hope that points to some areas to think about.
Cheers!
Regards,
Thom
P.S. I'll make a shameless plug for the static-control kit I make and sell for the Sharks. It's saved me and others from continued and repeated controller failures from severe static build-up. You can find the kit at:
http://thomr.com/2016/05/solve-static-i ... -machines/