There hasn't been much action on this sticky, so I'll add some advice of my own:

Replace some critical parts BEFORE they go bad, especially on a high-mileage bike.

This morning I went to the grocery store and on the way back the freehub body on my rear hub went out (It has at least 15K miles on it) and when I pedaled my bike wouldn't go so I had "scoot" it home with my feet. Since it was only a mile and a half away I was just mearly amused but I was horrified when I realized I could have been 30 miles away out in the boonies if I took that bike on a ride with my cycling club, which I have done occasionally.