HGTV confines itself to the last couple of years, when the renovations will still look relatively fresh.

What’s interesting to contemplate is how this changes the underlying economics of the network. Most networks that create a successful show can expect syndication revenue to make up the bottom line. That’s less true of reality shows, of course, but there’s still quite a bit of scope in a well-designed show. Food Network can run old episodes of “Chopped,” and they’ll be no less enjoyable simply because watermelon and feta salad is sooooooo 2012. Making a television show is like making a capital investment: Make the show once, and you can continue making money off it for years to come.

HGTV’s products, on the other hand, are essentially a perishable good. A 2008 episode of a kitchen renovation show has essentially expired. It cannot be safely aired.

Hence, a lot of reruns.