How often have you had your wheels checked or checked them yourself for consistent and correct tension and truing? If you've been keeping up on this I'd say that you're harder on your wheels than you realize or have let the spokes get quite loose between tuneups then yeah, a rebuild with new spokes is in order as these are just likely the first. But unless you've got serious warping, kinks or other issues with the rims then they should still be good. For example if you're using rim brakes then the rim sides may be getting pretty thin by now and the rim isn't fully spreading out the spoke loading or needs to be tuned up to allow for whatever shifting their is. Examining the rim closely for signs of eyelets pulling through would be another good idea. Once you're fully aware of the rim and hub condition if they are good in all respects then new spokes may be all you need to restore the trust in these wheels.