I can not address your specific situation, but I bought a 2006 Civic Hybrid new at the end of July 2006. Now, 23 months later, I find that the rate of discharge (and recharge) of the IMA battery seems to have increased. I don’t know if it is a temperature-dependent phenomenon or if the discharge-recharge rate characteristic changes with use (there are 16,200 miles on the car).
For example, on a given 100-mile round trip now (hilly, modest acceleration rates ? I have a light foot on the accelerator), the IMA battery monitor might go down 2 “blocks” or units on half of the trip and recharge that same amount on the other half. However, for the first 9 to 12 months, that same trip would cause only a one-block fluctuation of the charge rather than two. I have not documented this carefully, but I keep being surprised in recent months by how much fluctuation there is on the charge monitor. The instantaneous rate of charging or discharging, as shown by the other monitor seems not to have changed.