When my bid failed and I had been using 6 seconds, I checked with Auction Sniper, which is why I finally made my lead time 9 seconds. (5 seconds plus the 4 additioinal suggested during peak hours is why I chose 9 seconds). Interesting disclaimer on internet traffic...
Auction Sniper says:
64. What is the ideal lead time to use for a snipe?
Lead time is the number of seconds from the end of an auction that you would like AuctionSniper to bid for you. We recommend lead times between 5 and 10 seconds, although we've seen times as low as 2 and 3 seconds work just fine. Currently, Auction Sniper successfully places 99.9% of all snipes with 5 second lead times.
We don't recommend anything less than 5 seconds Although we send the snipe on time, during peak times an eBay server may not process it in time. This is not the fault of eBay or us; internet traffic is just heavier at certain times. And during peak periods, you might consider adding 2-4 seconds more since their servers seem to be taking quite a hit during that time (5-10 p.m. PST), and on weekends.