why is cgminer slowing down over time? I noticed something queer about cgminer, when I first started using it I got an ok amount of shares, but over time that number has been slowly dropping. it's the same difficulty,same temperature,but slightly less wu/m. it runs under the same conditions software  wise every day(i.e. no extra programs are running,Windows is not updating,etc) but yet it's still slowly dwindling away. not by huge chunks like suddenly stopping, but in general it's receiving less accepted shares(still 0 rejected shares, so it's not just failing at calculating them)
why is this happening, and is there anything I can do to help it?
It might be a signal your GPU is slowly decaying away, or may have to do with competition.

What coin are you mining, and at what pool? I've noticed that as more miners with more powerful machines enter a pool, they tend to give partial results very quickly so the pool orders a work restart more often - lowering the number of shares I get. If your pool allows you to manually set difficulty then set it to a lower value: better to send some shares for a lower difficulty than no shares at all.