I have numerous snipes that I've set over a several day period (from 1-6 day ending times). When I go back to check and refresh, I find they are now inactive and I have to reset and change/update the snipes. Then the next day the same thing happens.

Here are some items:
350455619025
380332591343
130510016305
Here are a couple that I missed because of the same thing happening:
380332301531
380332300109

You put those items into a Group with limit one item to win. So once one item is won, the other snipes are cancelled.
If this is not what you want, you should put "all" instead of "1" in the "To Win" field for your Groups. Or put "all" in the "Default To Win for Group" in Profile.
If you would've put your e-mail address, you would get an e-mail notification when your Group won as well.

Thanks for the info. Gotta say the items to win "feature" seems bizarre to me. Why would I put something into a group as an active snipe if I didn't want to win it?

The Groups are designed for those who want to snipe several items but need to stop once one (or some) items won.

For example, you need a cell phone charger. But you need just two of them only. You can find hundreds on eBay, so you put a few dozens to snipe, set your limit on "2" and wait until you get 2 great deals. The other snipes will be cancelled automatically.
If you want to win all items, you can set limit "all" instead.

Here are the links where you can read more about Groups:
http://www.myibidder.com/login/faq/2/#q10
http://www.myibidder.com/login/faq/2/#q11
http://www.myibidder.com/login/faq/2/#q12