I tend to post one a day, sometimes two, but I'm not a HUGE producer so I don't usually have a ton of items to list. I'll keep building up piles of drafted listings and list them one a day until I run out (and hopefully I'll have more listings to draft by that time). I post links to my new listings on facebook, and I don't want to irritate my "fans" by posting too often so if I only list one item a day I don't feel the need to be plugging my items multiple times per day. Does that make sense? (golly it's late, no wonder my own words don't make sense to me!).
But it varies for everyone. If you feel listing many things at once works for you, then by all means do so. But if you feel listing just a few a day works better, follow that route. It's your shop so it's ultimately up to you to decide!