"... what are people thinking is/are logical/optimal durations?"
I use either 5 day or 7 day and end auctions either Sunday or Monday night. I've also had sucess with 3 day auctions, but generally do not list this way. I started over-lapping 5 day auctions last year and that seemed to work the best.
From what I have seen, many people will not bid until the last few days of an auction. So I've never been inclined to even try 10 day listings. The counter argument to that would be that you can list a 10 day auction and have it run over 2 weekends which would mean increased exposure.
If I were listing a higher priced item I would try a 10 day duration.
In my opnion the problem with 1 day auctions is that not everyone is on their computer every single day so you could be missing out on a wider audience with just a single day duration. I guess the main point here is having a handle on how big your market sector is – I doubt that 1 day durations work well for me.
The above is only based on my experience - as you mention it will be different for all sellers.