Just please commit to it. I suspect organizations that use volunteers would rather have someone reliably there than someone who shows up a few times and quits.
That shouldn't matter unless the organization gives a clear expectation of the commitment level the volunteer would need to provide. Most places prefer any/all volunteers they can get (remember it's free labor and typically spawned by a person wanting to do something good for a community)
They still don't like spending half the time training people just to have them not come back. No one like a rotating cast of tech workers who show up just to make themselves feel better.
