The first time you do anything it takes longer.
Figure an hour for a COMPLETE oil change. That's engine, oil filter, tranny, and rear end. A good part of that hour is changing the oil filter if it's a cartridge like I have. That crossover exhaust pipe below the filter housing can get a little burny at times. Add a bit more time if you used an EMGO filter instead of the Russian filter.
Maybe a half hour just to do the engine.
Engine oil is every 1500 miles, trans is 3000 miles, final drive is every 6000 miles.
Valve adjustment is every 6000 miles, too. Figure an hour because the heads should be retorqued, too, and the bolts on the sidecar side are a bit hard to access. I just cut down a socket. Good thing is that the valve cover gaskets can be reused several times.
Once a year for wheel bearings and they're pretty easy, just messy. Shocks are rebuildable and usually just need a top up on oil. It's just that there are five of them.
Just figure on a major service every 6000 miles for a carbed Ural and maybe 3 hours if you aren't in a hurry. Can't answer for the fuelie bikes.
By comparison, major service on my CX takes just about as long because nothing is easily accessed.