Re: rebreather bag sizes and time of wear.
OK, first let me tell you I've had no experience with rebreather bags, but.........I would think that it s a bit of both. If you have a large lung capacity, a small bag may be the problem. Not knowing the size of tubing you are using, a .64 cm inner diameter tubing should be adequate, I've used that size on it's own as a breathing tube. One of 1.25 cm may be better.
There use to be a fellow who made masks that was a family member here. His pub name was s10. I would suggest talking with him if he is still around
Hope this helps!!
I'd rather be different than be the same!!!