Hi Kathy, 1. No gasket will hold up over time, just as no coffin will. 2. I have no idea whether the cemetery will unseal the casket. Given the lack of sensible knowledge about this I’ve seen in cemetery staff, nothing would surprise me. I would not, however, spend much emotional energy worrying about it. 3. Nothing is going to hold up forever inside a casket. If you want to be remembered, why not leave your personal effects and artistic creations around for the living instead of moldering in the ground?