Generally 1x per season for me, so roughly every 2500 to 3000 miles. A lot depends on the quality of the tire (the stock tires that come with some bikes can be pretty awful), how much wear there is, etc.

How did you flat? If there is a good-sized cut in your tire, I'd consider changing it. If there was little or no puncture I wouldn't worry with 1000 miles.

Also, it probably won't be there yet, but look for "squaring off" of the back tire. That's a good sign that it is time to replace.

If you're really nervous about the half, it certainly won't hurt to put new ones on soon. You can always burn the old ones on the trainer this winter.

It really depends on how they look to me. If I feel I am getting more flats than should be possible, then I will definitely change out my tires.

[quote=PJT]Generally 1x per season for me, so roughly every 2500 to 3000 miles. A lot depends on the quality of the tire (the stock tires that come with some bikes can be pretty awful), how much wear there is, etc.[/quote]

That's an endorsement. What tires do you ride on? Also, it depends on the quality of the road surface. I ride high-traffic shoulders and always roll through road debris. I get tiny little cuts in my tires all the time. If you have smooth country roads, you'll get several thousand. If you get mostly chipseal and shoulders as I do, you get 1,000. +1 on the squaring off, and do look for tiny little nicks and cuts. To extend life of my tires, when I get tiny little nicks (ie, 1mm long and not deep enough to go to the tube), I drop super glue down in there. If you visually inspect your tires and you don't have any deep cuts, you can do your half on them. Also, the location of the wear is important. If it's on the sidewall, that a weaker part of the tire because it's thinner and softer than the crown of the tube. I tend to not change tires before a race because I know the tube in the current set-up is seated correctly. I've gotten pinch flats several times right after I changed tires. I'd hate to change a perfectly seated tube and then flat in the race, not because of the tire, but because of my weak tubin' skillz.

[quote=TriSooner]

That's an endorsement. What tires do you ride on? Also, it depends on the quality of the road surface. I ride high-traffic shoulders and always roll through road debris. I get tiny little cuts in my tires all the time. If you have smooth country roads, you'll get several thousand. If you get mostly chipseal and shoulders as I do, you get 1,000. +1 on the squaring off, and do look for tiny little nicks and cuts. To extend life of my tires, when I get tiny little nicks (ie, 1mm long and not deep enough to go to the tube), I drop super glue down in there. If you visually inspect your tires and you don't have any deep cuts, you can do your half on them. Also, the location of the wear is important. If it's on the sidewall, that a weaker part of the tire because it's thinner and softer than the crown of the tube. I tend to not change tires before a race because I know the tube in the current set-up is seated correctly. I've gotten pinch flats several times right after I changed tires. I'd hate to change a perfectly seated tube and then flat in the race, not because of the tire, but because of my weak tubin' skillz.
[/quote]

Pro-Race 3s, and I ride 'em on basically everything.
I use a separate pair on race wheels too and, like you, I do not change those tires in-season if there are no flats. I had a disastrous first race a couple seasons ago specifically because of bad tube installation on race wheels. (3 flats and a DNF)

To the OP: If you do decide on new tires, do it now. That way, you can get several rides in on them and make sure that the tube is fully seated inside the tire and not caught anywhere under the bead. If that happens, the tire will blow. Violently. The bad part is it doesn't necessarily happen right away. In my race with 3 flats, I actually had the wheels out on a 20-mile shakeout ride earlier in the week and nothing happened.

The best way to prevent this is to install the tire and tube, inflate to maybe 15 psi, then push the bead of the tire in towards the middle of the wheel, first on one side, then the other. If you see ANY part of the tube sticking out under the bead, deflate and re-install.

Finally, be aware that some other flats have nothing to do with tire quality. If you have cheap rim tape that is worn through or badly installed, the tube can work its way into an uncovered spoke hole and puncture. This will keep happening until you fix the rim tape. Second, if you ride with an under-inflated tube and hit a pothole, the tube can puncture with a telltale snakebite pattern called a pinch flat. [url]http://www.sheldonbrown.com/gloss_p.html#pinchflat[/url]