KWA G19 using only Propane and Silicone oil had over 20,000 BB's through it. Finally broke a part and sent it to KWA for repair.
2 weeks and a little over $50 it was returned and totally rebuilt(including a new barrel) and is still running great.
In warm weather, I can get over 6,000 shots per Propane bottle at less than $3 per bottle.
I have other AirSofts that I use the same in but they don't have nearly the BB's through them as my #1
I gave my Grandson a KWA G19 several years ago and no telling how many BB's have been through it and it is still going great.
He uses the same Propane that I do.