Hi Carly,
Each year I remove the (old previous season's) top portion of the mix and admen the remaining soil with some Vermont Compost Container Booster Mix
https://www.gardeners.com/buy/... that I get from Gardener's Supply.
I also mix in some Eco-co® Coir
https://www.gardeners.com/buy/... that I also get from Gardener's Supply.
This way, I don't have to use all new potting mix for my containers each year.
I then, add some of the new and fresh (yellow and green bags) Miracle Gro potting mix on the top.
https://www.miraclegro.com/en-...
Since last spring, I been mulching the top of the containers with mulch that I get from Gardener's Supply
https://www.gardeners.com/buy/...
Several containers are extra-large black "nursery tree" plastic pots, some are 24 inch plastic containers, some are 20 inch plastic containers, some 17-20 "hard" plastic gallon tubs (the kind with white ropes for handles) that my husband drills 8-10 holes at the bottom that I use for containers, some are 16 inch plastic containers, a few 14 inch plastic containers and a couple 15 gallon black plastic containers. With the size of them and the mulch, I don't feel I have to water too often (once a week, along with the rain we get). I water a lot more (twice a week) when it's very hot. I have a 36 inch watering wand attached to my hose and water them deeply. (big drinks of water)
I leave all my containers outside 365 days of the year.