I'm still using 8 of these I've had since the early 1990s, so there's no issue with their longevity. They help to even out temperature fluctuations within a day, but don't do much to more sustained changes, so if the place they're located in is subjected to extreme temperatures, the benefits might be limited. Having said that, bottles I've had stored in these in an insulated garden shed for up to 20 years generally have corks in very good condition. The only real downside (apart from the cost) is that wide or tall bottles don't always fit in the holes.
How much are they selling for now?
Edit: link to an earlier post of mine discussing these:
http://www.australianfrequentflyer....inomofo-wine-deals-53217-513.html#post1312358