Mine were new in May 2009 and worked well when I put her to sleep for the winter. Coach is plugged in to power year around with the BIRD keeping the house and coach batteries topped off. I expect it will start up just fine in April or May when I can get it out of the barn. If it wont, I will boost it from the house bank and then replace. The house batteries lasted me eight years so I expect in the next few years I will be replacing the chassis batteries. I will not replace until they fail as I can't be left stranded if the house bank is available. I also carry jumper cables so I can use the toad to charge either bank as needed to get something running.