Prius (2004-09) :: Fill Up In Ready Mode - Gas Capacity On Bladder Decreased Significantly

I used to fill up with gas without shutting the car down, because I didn't see a need for it. I would disable the fan on the climate control every time to avoid having the ice come on as I refueled. I figured that because the ice wasn't coming on, I wasn't breaking the law. I've since changed my mind about this, after reading posts here on Prius Chat. I also recently noticed on the last few fillups that it seems like the gas capacity on the bladder has decreased significantly.

I used to be able to refuel the car when it was down to a single flashing pip and put 10.5 gallons in with no problem, and without overfilling. I have always been careful not to overfill. However, it seems like now I can get only 8 gallons in at the most. The capacity has decreased with the colder weather, however I used to be able to get 10 gallons in on a consistent basis without overfilling even during the winter.

Is this reduced bladder capacity a result of damage to the system, or is this normal? I have probably filled the car up about 100 times since I've owned it (odometer is around 50K now) while remaining in the ready mode.

Is there anything I can do to expand the capacity of the bladder back to normal, or will I have to live with this? Although it's annoying, I'm not going to spend the money to replace the fuel tank unless it's truly necessary.