While we don't see experimentation with Pym Particles, we do see experimentation with Cross Particles. We see Cross zap (for lack of a better term) various subjects with Cross Particles to (attempt) to cause them to shrink.
Do the usage of the Pym/Cross particles use up the particles? Do the suits supplies of particles need to be restocked?
Yes, it does. Cross, at least, makes this explicit when he
sells the suit technology to HYDRA.
He specifically points out that he's keeping the secret to the particles to himself, so any prospective buyer of the suits will need to come to him for the "fuel" that runs them.
There are also other, less obvious indications that the particles are somehow used up. In one of the early scenes with Scott, Hank can be seen "refilling" the reserve of particles that is kept in the suit.
