A short handling time is among eBay's "best practices" list, which are usually meant to influence best match rankings in some way, but like pretty much everything, user experience doesn't always match the info from eBay... 😄 (eg most sellers will tell you when they switch to free post, or adjust listings to qualify for premium service etc, or anything else that's supposed to either boost rankings, or lower them, they've not noticed any real difference). 

Handling time really now only affects the buyer's initial expectations when they make the purchase decision, as eBay will adjust it based on when it's marked as shipped.