Currently when you post an auction as a BIN/auction, when someone bids on it, it will automatically change to an auction that will run out in 3, 7, or 10 days. You can then have up to 10 reposts before you have to repost it yourself. Under the current system, it is very difficult to figure out which auctions have run out from the ones that haven't.
I would suggest that for seller + Lifetime subscribers the auction should stay posted as a BIN/auction as long as you sign in and keep you account active per eBid policy. If someone then bids on the auction, it should expire according to the previously selected 3, 7 or 10 day period.
BUT, if you're not seller + Lifetime you should have to repost it every 3,7 or 10 days.