the time of day to end your item depends on the type of item. more adult things like furniture,tools, carparts etc. are better around noon, when the majority of buyers are on their lunch break. for things like video games & collectibles, a couple hours after school breaks out is good. for things like blankets, womens things, early evening is good.
i agree with kami33, that antiques and rares should be listed longer than common things.
remagavon is right with the fact that extending the bidding time after a bid kills the whole idea of trying to find a deal. also too many businesses are coming to ebay and setting up shop. they usually put ridiculously high reserves or opening bids on items, that are inflating the whole market. couple years back, it was the norm to find brand new $50 games on ebay for like $35. now, half the sellers online are businesses, & that same $50 game closes for $48.