I have a SMK CP1-M - the manual is very clear that you should never leave the CO2 capsule in for any length of time and tells you how to discharge a partially used one.

The consensus from some very experienced club members is that the neck end of the capsule will flatten the seal which will eventually fail to re-seal. A drop of gun oil on each capsule can help keep that seal pliable.

Like everything else we all have our own ideas and practices, go along with what you feel most comfortable with, good luck and enjoy.

M.