The delay is due to the time it takes WoW to write all of your saved fight data to a file on your computer's hard drive. It is not a bug in Recount, and there is nothing Recount can do to make your computer faster. You can decrease the delay by:
(a) clearing your fight data before logging out,
(b) changing your Recount settings to store fewer fights or less data (for example, storing time data adds a huge amount), or
(c) upgrading your computer's hardware.