how long?

[IncognitoIsMyFavouriteWord]

How long is a reasonable time before you post the item?

if a buyer is an instant payer when the auction has ended?

I usually post the next day unless its a Wednesday. My post office half day closing on a Wednesday.

I was just wondering about everybody else

My terms state within 3 working days of receiving cleared payment, so always inside this. Next day if at all possible with work/kids etc. Sometimes same day if they get the payment to me in the morning and I'm at home.

Same day or next day. But I have a post office a few minutes' walk away. Might be a different story if it were miles away, with a storm raging.

What's reasonable is what you state in your terms on the listing.
I tried to offer next day posting for a while but it was too nerve-wracking.

for most people posting second class what is in your terms but 48 hours is reasonable ( not including weekends)

I state on my listings that i post within 48 hours but not wednesday, or weekends ( generally if paid before 7am will be sent that day)

however if you offer first class posting you really have to post within 24 hours, do not offer 1st class if you can not post every working day

to post 1st class 3 days later is just not on, people pay extra for first class assuming quicker,,

most people do not read dispatch times they assume 1-2 days so if you only post once a week on thursdays you must make it very clear in listings to avoid complainants