Doubt it means "failing". More likely the air-charge portion within the tank has diminished and needs to be re-balanced. If so, it's a normal occurrence over time and, although annoying, easy to fix. If it happens really often, that would indicate failure and time to replace.

Thanks asolo,
Can we charge it ourselves, or is this something a professional needs to do? I know there are warning stickers all over the tank. Its a big tank.
Thanks.

Like most things, it's easy if you know what you're doing. Without being personally familiar with what you have, I'm reluctant to give any opinion about what you should do. Especially in view of your warning stickers, perhaps it might be best to hire done. In any event it shouldn't take long or cost much and after you've seen it done once, you'll know what to look for and what to do next time. I don't like expense but I don't like worry either. Maybe look at it as the price of a lesson you'll be happy to have learned.

Good advice asolo! Thanks again.