How often do you change them? do you see wear or change them after so many shots regardless? thanks, TVC15

Think you've answered your own question there TVC15.
As loops are straight forward to change ,then go ahead and change the loop if its bugging you.
Personally I have changed one in the past 4 yrs of shooting.
That loop told me it wanted changing by letting go one day. as I carry a spare in my bow case it was quickly replaced and 10 minutes later i was shooting again.
Wish all things with bows were as quick to fix.

You definitely have to check for wear on the string loop. Any sign of wear, measure the centre of the loops location on the string and then simply replace it. I have on three occasions seen the jaws of the release allow the string loop to slip through and cause a release when the hunter was on "partial draw."

The jaws of a release also wear with age, even though made of metal.

I have a thicker loop on my bow and have changed it only once in a year. (I shoot at least 120 arrows a week - 480 plus a month.)

Soroko, brings up a good point. Release type definitely affects the life of a string loop. Caliper style releases being the absolutely hardest on loops IME.

Also the cord used for the loops comes in varying grades. Don't skimp on it. Cheap loops don't hardly last at all. Brownell makes good loop material. Usually you can buy a a foot of the stuff at a decent proshop. Good quality loop material and a less damaging release (like a Fletchunter or Carter Quikie) and one loop can honestly outlast the bowstring.