I am deeply understanding wickidwombat: to have a (or two or three) spares is always necessary.
And with the double slot on the 5DMk3 this camera got professional in my mind: no worries about a corrupt card or file.
BTW: 16 and 32GB seem to have the right capacity for raw. 500 up to 1000 files are not too much to remember a bit of the non- exif data in my memory, not too less to shoot something important and dont want to change the cards.
1D MKIV, 1DX MkII, 5D Mk IV; lot of lenses, flashes etc
Fuji X100s, Sony RX100 III,
Fuji X- XT1, X- Pro2, XF 23 1,4, XF 18- 55 2,8-4, X- T1, XF 16/1,4, XF 55- 200, XF 56/1,2, XF 50-140, XF 100- 400