There may be something up with your compressor - not sure if that was mentioned before.
Because CFer's are such heavy compressor users, the machines can go out sooner than the average 3 years.
If you have a PARI compressor, you can always call them and get the compressor swapped out for a new one. It's a pretty painless process.
You are very wise to keep on top of treatment times - this is often the first indication that something might be up.
My philosophy is - if I'm goign to be investing time in doing treatments, everything better be at top performance. Otherwise, it's a waste of time!