Hindi ako sure exactly kung gaano katagal ang Bona formula after opening kasi depende sa brand at storage, pero usually most formulas last around 3-4 weeks once opened kung refrigerated properly, mas safe pa yan i-follow ang instructions sa packaging ng specific brand mo. I'd suggest checking the can or box for the manufacturer's recommendation, or better yet, contact Bona directly para sigurado, kasi iba-iba talaga ang guidelines!