Switching to a corded grinder, will be like night and day. Cordless is more convenient, but the plain old grinder has much higher rpms, and way more power. I have a 4" Makita that I bought years and years ago, I routinely run it until its so hot its not comfortable to hold, then let it cool off. Its amazing how long they last, if you just check the brushes now and again. You can always get s sweet deal buying at a garage sale too, just buy something that's a "good" brand, and that you can get parts (brushes) for.
