We bought an inside-mount VSB doorkeeper complete with the VSB door, sensor, and timer from Foy's back in July 2008. It worked flawlessly until this past summer, it began opening and closing at the wrong times until it just stopped altogether. We changed batteries several times and called Foy's for troubleshooting assistance, but nothing worked. (BTW, the unit was completely free of dust/debris on the inside.) Finally, we mailed the unit back to Foy's to see what could be done. Well, Foy's called this week to inform us that the unit is shot and that we needed to buy a new one. The unit was not cheap when we bought it 4 years ago - we paid $160. Now, the price for the unit is $212! Do you think 4 years is pretty much all we should expect a VSB doorkeeper to last?