If one of the tires has died a natural death, i will change the pair, just for the convenience factor and down time.
However, if I had pretty new sneakers on the bike and I blew one out, or put a hole in one, I probably would replace only the affected one.
Tires are no cheap proposition on the Wing. Number one, we pile up some pretty good miles on them in no time at all. And the average life a tire has been somewhere between 11K and 15K. If it were not for Hals' great prices, I think that I might try to stretch another mile or two out of them.
Another factor that plays, is seasonal need. Myself, I like to start out in the spring with no down time. Heck I just came out of hibernation. As the summer progress and if I get into fall, I will change again if necessary. I usually only get 8K to 12K on the wing in one season, even with a long trip. So I am pretty much a one set of tires a year guy.
Please do not ask me why I have brand new sneaks on the bike right now, and 3 brand new rear, and 2 brand new fronts in the garage attic. I don't want to name names, but it is Hals' fault....LOL
Ok, i got to go. I have to get ready for a meeting tonight at 9:30...LOL