You need to keep recruiting volunteers, even if you have enough.
Almost 6 years ago I used to be involved with UKT, a community for fans of online gaming. It was a strong community with thousands of registered members and a good number of volunteer helpers.
After 4 years of steady growth, the community collapsed within 6 months. The reason was we stopped recruiting volunteers. We felt we had enough. We stopped recruiting, training and even trying to properly motivate the volunteers we had.
Volunteers don’t work for free, they work for fun. Which means they will volunteer their time until they find something more fun to do with their time. If your volunteers are young, this can be a major problem during the summer.
We didn’t spot the problem until it was too late. A few volunteers left over two months. The remaining volunteers worked harder to cover. The extra efforts without rewards took it’s toll and they left too. The result was a sudden stop to the fast-paced content.
Volunteers wont stick around forever. You need to continually recruit more.