The checkbox is for moving or deleting an item, bing. It makes it convenient to take a similar action on a number of snipe setups at once.
Five seconds is usually an acceptable lead time for a snipe but your risk of the bid not being accepted in time by eBay increases geometrically with every second less than 10. I use 8 seconds (except on Sundays and certain auctions; see below) which is plenty of time in most cases but certainly not enough time to allow someone else to counterbid.
Sundays are eBay's busiest times and so many bidders are active that eBay's servers often can't keep up with the load. While AuctionSniper tries to allow for that by monitoring eBay's server reaction time and adjusting the lead time of your snipe accordingly, it really helps if you allow not less than 15 seconds for a "Sunday snipe." There's a limit to how much AS will adjust your snipe, so help 'em out a bit. Remember that proxy bidders are faced with the same eBay lag in registering bids that you are, so you're not tipping your hand too early.
EBay allows sellers to select the opening -- and therefore the closing -- times for their auctions. So many sellers choose to start on an even hour, half-hour, or quarter-hour (XX:00:00, XX:30:00, XX:15:00, or XX:45:00) that once again eBay's servers can't keep up with the rush of bids in auctions ending at those times. Allow at least 20 seconds lead time if you're bidding on an item that ends at one of those times.
One other thing:
always bid your maximum amount. With sniping you only get one shot, so make it your best one. One of the hardest things new snipers have to learn is to get away from the one-increment-nibble "proxy" approach to bidding. Come in out of nowhere with 5 (or 8) seconds to go and blow 'em away. You'll be glad you did.
Happy hunting!
