I often bid in the last few seconds for the same reasons already mentioned, budget, sometimes it keeps the price down etc.
Except if the item is a fairly common thing I usually place a lowish bid and let it go.
Sometimes I bid late because the items are so uncommon I can't even find a comparable item. A couple weeks ago there were some really uncommon covers I was interested in for my stamp collection. (Envelopes with stamps and postal markings if someone doesn't know the term. )
I got blown away on the first couple, lost by a bit on the next couple and went pretty high winning the last one. I was really glad to get it, it's the only known pair of that stamp on cover, and one of only 28 covers with that stamp at all. (Not counting maybe 2-3 where it's mixed with even less common ones. )
And it's from a famous collection. Not usually a big deal to card guys but a bigger deal in stamps. The best part is that there's apparently been no recorded public sales since the Ackerman collection was sold off in the 1930's
First collectible I've ever charged. And only because I knew I'd never get another chance at it.
If I'd bid early on all of them all the bids would have probably ended up being really low bids and I've have gotten none of them.
Better still one that I think is rather special slid under the radar or got lost in the bunch of better stuff and I was the only bidder.
Maybe someday I'll have the budget to place solid bids on a bunch of stuff, but till then I have to pick and choose.
Steve B