It’s possible. Instead of there being perhaps a 1 in 10,000 chance that the snipe will be too late, with a shorter lead it might increase to 1.001 in 10,000?
Most of the posts on this forum are from users, and users don’t have much in the way of statistics. My guess is that there are probably a lot of users that specify a 3-second (minimum allowed) lead time, and based on the lack of complaints on the forum about not-in-time snipes, I’d conclude that 3 seconds is just as good as 5 or 10. So, your preference is just as good as the next sniper.
About the only complaint about errors in lead times is when someone specifies 3 seconds and the snipe is placed 6 seconds before the end of the auction. So, if you’re the type that would get upset about this, then use a 6-second lead time.
If you want info from a more informed source, then try this:
http://support.auctionsniper.com/
p.s. Don't sweat the lead-time. That's what AS is paid to do. Spend your time deciding how much you'll snipe and on which auctions.