Hi David,
When I was starting my business I got onto a free course that had a few consultants doing mentoring on it. One of them recomended that I try to figure out who my customers would be and do everything I could to place my product in a way which would appeal to them. He recomended that I do a brainstorming session, talk to potential clients, do market research, run surveys etc, all to find out what the client wants, and when, how fast, what price etc etc. He told me there was two types of research live (face to face) and desk(newspapers, internet, library etc).
I don't know a lot about handbags but the priciples will be the same as for most other products. I would first of all look at my current online sales, see if there is any trends, I'd look at offline trends if there is any. Check what your competitors are doing, on ebay its pretty easy to see how well they are doing, use a site like goofbay dot com to help with that. If you can identify information that you need there are survey sites that you can use to gather the answers, offer your clients a freebie or prize if they will take part. How about starting a forum on your site or visit forums on the subject.
I could go on like this for hours.
Anyway your original question about times to end ebay sales. I have two target markets, retail type clients, I prefer to end these sales at the weekend (Fri, Sat, Sun) generally in the afternoon or evening. The second is the business type and I split this into two types 1/ Employee buying for the company, i'll expect them to buy during office hours, afternoons normally, 2/ Owners or managers of smaller companies, They will more than likley buy late evening or later (after they finish the important work and get a chance to do something a bit lighter - like i'm doing now)
This was supposed to be a short answer - I failed
Good Luck
Jim