How long a plastic painter's drop cloth will last as a footprint depends on the thickness. The thinner it is the lighter it will be to carry, but also the more vulnerable to damage and the more quickly used up and disposed of. I use a plastic 3 mil footprint, cut to size, under my car camping tent, which helps to keep the bottom clean and gives a bit of extra protection. But that is for car camping, where the extra weight and bulk of a footprint is negligible.

If you are taking a footprint on a backpack, then the more fundamental question is: why should your tent floor need a footprint under it?

From my point of view, if it needs a footprint to keep from leaking, then your tent is not very reliable, either because of age and wear or poor materials and workmanship. If the tent floor is watertight, then usually a bit of care in removing sharp objects from the ground where you pitch it ought to maintain it in good shape. In my opinion, tent footprints for backpacking don't justify their weight, no matter how light they are, so that personally, I do not carry one with me.