IME a bubble counter is a rough visual guide of the amount of co2 delivered to the tank. Once you have enough experience with different layouts in the same tank, using the same kind of water, light, etc. you pay less attention. I used to measure every few months my pH profile to adjust the bubbles, and now with 2 new setups I have not done it... And they are running for 6 months now.
For me bubble counters are a way to have a fast assessment of basic things such as: there is enough co2 in the cylinder, it looks like the bubble rate is as it usually is, if I've been away for a few days I can see that everything is ok... This is why I have my bubbles counters always outside the cabinet. I can see them when I come home, when I'm on the coach, etc.
Unfortunately the co2 performance does not depend only on the bubbles per second, but on a few more things. Only working on each of them and keeping C enriched tanks will give enough experience.
Jordi