You can adjust the handling time in your listings, it's in the shipping details section when you make or revise the listing, the default is one day. I upped mine to 2-3 with covid.
I upped my handling time to 10 days and eb was still giving a delivery date to buyer in 12 days from purchase with First Class Shipping. 10 days for handling and 2 days for shipping. My First Class packages generally take 4-8 days to get to my buyers after I ship them.
It may not help to increase shipping time. I have always had 3 days. Last winter I had several little things that I was selling with free delivery. eBay added “ free and fast”. I was told that because I usually shipped fast it was added. I add extra time in case an emergency happens.
eBay puts delivery estimates in every listing (unless it's freight or pickup only). When you look at your own listing, you are shown the estimated delivery time to a buyer in your own ZIP Code. Go to the shipping tab and experiment with a ZIP Code on the opposite coast.
