I have never found a reason to believe that any of the sales we had attributed to campaigns wouldn't have happened without the campaigns.

I think it depends a lot on exactly what it is you're selling. I'd guess campaigns have a bigger affect on high value items.

Yes last week i turned mine off for 3 days last week as wanted to cut my orders down to have a little break and now ive turned them back on im getting nowhere near the amount of orders i was. I probably wouldn't advise doing it. Just lowering the bids

Low Bid Campaign - Have you tried this?

Instead of completely pausing ads, have you looked at pausing them or reducing the daily spend during your off-peak trading times? I've started limiting ad spend at the weekend (when we have fewer orders) and using that budget during our busier days during the week). It's not really impacted our weekend sales and we've had a much better month for ad sales overall.

We did a test and the sponsored products are between 25-30% of our sales so we continue to use them all we can.

Usually it stays neutral for a day or two and then the sales decline starts once ads are paused unless the listing is really old and ranks organically extremely well for very long.

I did it last year on other bigger account with well established organic positions. Not much difference in the 1st week, then sales started to slowly decline as there was less traffic to listings -> lower sales velocity -> lower rankings. I un-paused ads after about 2 months, when it was clear that lack of ads not only hamper my growth, but actually influence organic positions and sales started to decline across the board. It took about 1.5 months to get back to where I started, one might say I've lost 4 months of growth with this experiment.