Mine is on charge around 80% of the day, yet maintains it's original battery life when it's running off its own juice.
I don't see a problem, the only issue I can think of is that using the phone heavily whilst on charge causes the battery to heat up and this can sometimes be felt through the phones casing.
Sent from my C6603 using xda app-developers app
If it's broke, use a hammer. If that fails, you're not using a big enough hammer.