Well in order to stay on top yes I would probably say once a week the least! thats why I quit uploading three months back dont have the time for it nor the patience.

What happens is that the few that sell immediately from an upload are pushed forward and the ones that dont sell are gone. I personally have never noticed a drop in earnings from not uploading but many say they have.

I try and do twenty a week sometimes more (photos). Whether it makes any difference I couldn't honestly say. But it kind of spreads the risk/reward of being buried or submitting on a favorable date. But mainly it keeps me sane by not working 25 hours a day for peanuts.

Around 100 images per month but it's pointless nothing sells on SS anymore just old stuff

I used to upload Pictures almost every day. Like 1000 per year.

Not so anymore.
it simply doesnt pay, I am better off growing cellery in my back garden.

I used to upload however many pics I had ready (none to 20 plus a week) to SS to have them accepted Sun night / Monday morning. Of course that timing  didn't always work out. Now I still try to do that but with less success and care - more like Mantis - I upload the pics I want to when I feel like it. I don't think this helps my income any, but the big drop was while I was still uploading. From time to time I get inspired to do more work, and sometimes I am busy with other stuff and ignore stock (at least the processing and uploading) for months on end. (this is 99% photos). As far as I can tell the number and timing of uploads only has a vague and long term effect on my sales. (unlike years ago when uploading a batch of images would result in an immediate bump of sales of those images and perhaps older ones too).

The timing on SS has been weird lately - uploaded Sat evening - accepted in minutes. Uploaded Sun Morning - partly accepted Thursday afternoon. So much for that batch.

Perhaps I should try the PixelBytes strategy.

Zero times a week. I stopped uploading when I stopped seeing results.