I think it's best to list one at a time for more traffic into your shop. I saw in a different post in this Team that there is/are best times to post but I can't remember...
I try to be posting or renewing an expiring item once a day. I also findnthat most of my sales are in the late evening so that is when I try to list since that is when my target buyers seem to be shopping
I curate vintage and try to list at least once a day. Living in Hawaii and with our unique time zone, there are challenges, so I post between midnight and 3pm, when the rest of America is already up and running. It seems to work....
I list one item a day. I try and list it as late as possible so that people are actually on here shopping to discover my new item, instead of listing it in the morning or afternoon when people are at work. If I have more than one item ready to go I wait to list the other items to spread out my exposure.
Sometimes I get my listings done at a time or day when I have a few that have expired. In that case I'll just draft my listings and wait to list them. I don't like to have everything list or renew at once. I think it gives me better exposure to let it all ooze out over time.
I think a few a day. If you don't have time everyday, list them when you do have the time and save them under drafts. Then once a day list one from your draft selections and it's done!
I usually take a bunch of photos in a day and get them up, and I try to do it a couple times a week. I do think it's beneficial to add a couple of items a day instead of all at once. I just get so excited when I finally find the time to do it and I list everything. :) Patience is a virtue.