My feedback has dropped to 85%! All becasue one buyer didn't like the fact that her dress arrived,in her opinion, late

[Saltire]

I clearly state that I do most of my posting on Fridays or Saturdays, becasue these days I have a spare 30-45 minutes to stand around in the post office waiting to get served.
Anyway, dress sold on 29th May ( a friday) and was paid on the saturday. So I posted it the following Saturday,which I what I say on teh ebay listing. She says she emailed me lots - she did twice, each time I pointed out the reference to posting in the listing! SO now, out of about 9 feedbacks, 1 negative has dropped by score. All the others say the item arrived quickly and didn't have a problem!

no you noo-noo - that's Paypal (yes I know they're the same company but still) rules if you want to be protected by paypal seller protection .

My DH sometimes buys games that are on pre-order so maybe that's the sort of case where you have longer to post?

If I were you I would start timing your listings (I think you can delay when they start when you list) to coincide better with your schedule.