I used to make it a point to start long tours with new tires, but have since started just replacing them where ever I am as needed. I found that once I took them off I never used them again and it was a waste of expensive tires. That might mean I have less choices at the time of replacement, but no big deal.

I do the same for brake pads, but if a tour is in the mountains I might carry a spare pair or change them before I get go.

If in doubt you might want to make sure that all of your bearings are OK and not in need of repacking. Maybe also check cables for fraying at or near the ends.