I use yongnuo transmitters / receivers and I kid you not that in general the cr2 batteries that I buy for them last me about 2 wedding seasons, so 30ish weddings, thousands and thousands of shots. The AAA's last maybe 7 or 8 weddings at minimum. That said, I'm not using ETTL versions.

One thing I would recommend if you're not doing this already: for wireless triggers use alkaline batteries and not rechargeable.

If you're getting only 20 photos using new alkaline batteries, yes, there would likely be something wrong with your wireless kit.