Small cog in front (I've got a compact double), Cassette and Chain
With lots of riding in all weathers, any of these things could need replacing in the timeframes you've given.
This lot, however, seems a bit less run of the mill...
Wheels (bearings are worn out)
If the bearings are worn out, then the hubs should need servicing, not the wheels replacing...
Rear Derailleur
What exactly did they say was wrong with it? And have you actually been having trouble with shifting? The jockey wheels on RDs do need replacing from time to time, but the whole unit rarely fails unless it's been knocked hard/crashed.
My opinion? Get a second opinion, and bear in mind that you could do everything except the hubs by yourself at home with no special tools other than a set of allen keys. And a little patience.
Drink coffee and do stupid things faster with more energy.