Of the 25 volunteers in my training group (Malaysia 50), none that I’m aware of had any serious volunteer background. Most of us were fresh out of college. We had science and math skills that the host country needed. That said, nearly half our members dropped out during High Intensity Language Training (HILT). A few had difficulty adjusting to the food. Many struggled with rote memorization of (to us) meaningless dialogs. I do not think any previous volunteer experience would have helped lower attrition. Other factors were much more important: tolerance, flexibility, perseverance, determination.

Thanks, that answers my question!