- It depends on how fast you go through it, if your tape rolls last you longer than a month then sealing them after use is good practice. Otherwise there isn't enough time for the tape to degrade in the open air. I go through 1-2 rolls a month, so sealing them isn't necessary.

- I found regular masking tape not to be as effective as painter's tape, is the automotive masking tape similar to painter's tape? Would you have a link to some?