Before I moved to TN, I ran with a volly rescue squad in Northern VA. We were one of 3 squads left in the county that was still 100% volunteer.
We had similar problems getting people to respond. If they weren't choosing calls, they just couldn't get the time off from work and family to run. A large part of the problem was all the new residents moving into the area who didn't want to volunteer. They bought 500,000 dollar houses and sure didn't want to leave in the middle of the night to go carry aunt bee to the hospital because she decided that the breathing problem she had for the past week just couldn't wait until the morning. :p
We had scheduled duty nights that we covered, during the day it was somewhat of a tossup, depending on who was in town. Like you we had a volly regional medic at nights, paid county medic during the day.
Sadly, after I moved, the stationed had to request paid staffing during the day. The call to volunteer is getting weaker with the newer generation, and people aren't wanting to spend their time helping others without getting paid for it. I loved volunteering, and I'd do it again if I could find a place down here that wasn't 100% paid.
As far as a solution to your staffing shortages, you'll have to get together at the monthly meeting and lay it on the table. Either people step up to the plate, or paid staffing will be requested. Most volly's don't want to give up their equipment to paid staff unless neccessary, hopefully you'll be able to get people to run more calls.
Good luck bro.
911 Fire/EMS Dispatch
Volunteer Fire/Rescue
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DAN: If guns cause crime, then pencils cause misspelled words, matches cause fires and spoons make Rosie O'donnell fat.