I asked the dealer who looks after my bike to replace the rear wheel bearings before my Euro trip last year, including the needle roller (gen. Yam. only part?), but they said that on inspection, the bearings were fine. They did the trip ok, and many miles since.
The reason I had asked them to do it, is that I have had them fail on a previous gen 1, at a similar mileage to what this bike was on then. I was a bit annoyed with them, as even if they didn't need it at the time, they didn't carry out my instruction, which I was happy to pay for.
On the recent service, one was discovered to be on the way out, so it was replaced. But should I have asked them to replace all of them? Would a failing bearing have put strain on the others in the wheel? The upcoming trip could extend to more than 3000 miles, so I'm a little concerned.