Do you get a lot more footage / spin hours on your other blades? Or is it just a few more?
Ken Cook from Cooks' saw wrote a nice article about grinding gullets, and his conclusion is that it does not help at all. I went to school for Engineering and agree that it can't help. Cracks in the gullet are the result fatigue that results in stress cracks. Grinding out material will not help that, and in fact will accelerate it, since there's less material to resist the stress.
Welding on the other hand would seem like it could help, but you'd want to fill the entire crack with material, then grind it flat again, to avoid "thumps" as the band goes around the bandwheels. Basically just like welding up a new blade. This would make sense on a relatively new blade, but not on one that has been through several saw - resharpen cycles, since there will be many fatigue cracks that developed in many of the gullets.
What size bandwheels does your mill have, and have you checked to be sure they are "co-planer"? I had a real problem with band life until I took some time to align my bandwheels and make sure they were both perfectly in line and in the same plane. I wrote up how to do it somewhere here, so just search a bit to find that.
Best of luck.