hi, that may in fact be the case. Places like Radio shack should have battery testers that they can run on the battery and tell you if it really needs it or not. Do you have corded wired telephones, or all cordless phones? a replacement battery may not do you any good if you have all cordless.
Actually, yes, we have all cordless phones right now, but I want to get a corded, so I'm having a couple of additional phone outlets added during the rennovations. But we use the backup battery for other things - we have FiOS TV and Internet too, and the battery can keep those going for a little while in the case of power failures or brownouts. (I have my computer and wireless modem also plugged into a separate small uninterruptable power supply.)
Thanks very much for the suggestion about testing the battery. I will definitely do that before I buy a new one. I'm looking at getting one - if I need to - from someplace that sells UB1270 batteries for $17 or $18 on Amazon. I'm not sure if the connectors need to be F1 or F2, though, or if I just pull the current ones out of the existing battery and use them with the new battery.
I wanted to let you know that you can see a quick how-to video on how to change your back up battery here. The video is under 2 minute and it'll be well worth your time if you have go through this again!