The past three years I have bought new potting mix for my containers.
I dumped the previous years potting mix into my raised bed and RotoTilled it in thoroughly.
It has really helped the heavy clay-based natural soil in my raised bed become an excellent growing medium.
I have used Sta-Green MoistureMax, Fox Farms Ocean Forest, Fox Farms Happy Frog, Pro-Mix BX, Dr.Earth All Purpose Planting Mix, and Miracle Grow Moisture Control Potting Mix, some individually, some in various combinations.
I would guess in the three years I have added about a cubic yard to my raised bed. Yes, it does tend to spill over the sides, but it disappears into the lawn.
This year, I am setting up a 100 gallon BigBagBed and ten 10 gallon fabric grow bags, which in all will require approximately one cubic yard of potting mix.
I intend to go with a mixture of 3 bales of Pro-Mix General Purpose (expanded to 4 cubic feet each; 12 cubic feet), 5 bags of Happy Frog (two cubic feet each; 10 cubic feet), and 4 bags of Ocean Forest (1.5 cubic feet each; 6 cubic feet).