Never (not in fifteen years on my current bike riding 3500-4000 miles a year now with 1500 miles of commuting putting a lower bound on my annual total. That includes ten years in Boulder, CO with snow and a handful of car free years).

More specifically you want a continuous maintenance program where you adjust (cup and cone bearings are pretty much the only thing which need adjustment unless something is wrong), lubricate, and repair or replace as necessary.

There are too many variables there to put time or mileage bounds on most things (ex: some people get 1500 miles out of chains, some people get 5000), nearly everything gives some indication of wear (for example, shift cables get broken strands where they join the shifter) when it's time to deal with them (much better than waiting until you're riding home in one cog), and that happens over radically different time periods for various components.

Greasing cup-and-cone hubs every 3000 miles is the only thing I put on a fixed schedule. Other things happen at convenient times - for instance when my chain ceases being silent I need to lubricate it and take the opportunity to measure it at the same time. I preemptively replace my right shift and front brake cables at the same time as worn Campagnolo shifter G-springs because the cables need to come out anyways.