Shuttering plywood is a site investment — the more clean pours you get from a sheet, the better your project economics.
Apply a release/form oil before every pour; it's the single biggest factor in preventing concrete from bonding to the surface and tearing the face on removal.
Clean sheets immediately after each strip — dried concrete residue is far harder to remove and damages the surface over repeated pours.
Store sheets flat and covered between uses. Stacking upright or leaving them exposed to sun and rain between pours warps panels faster than the pours themselves.