Replacing things like windows, major appliances, or roofing can get expensive.  It's important to know approximately how long you have before the water heater goes out or the roof springs a leak.  This is important information for both Buyers and Sellers.  Buyers may want to factor in replacement costs to their purchase offer price if there are aging components that will soon require replacement.  The flip side of that concept is that Sellers should consider these factors before placing their home on the market as well.  Sellers should consider whether or not it would be to their benefit to replace the aging components prior to having the components become a point of negotiation with the Buyers. 

A recent study by the National Association of Home Builders provides some insight that should help you estimate the average useful lilfe of more than 100 household appliances and building materials.  Of course, the true longevity of any household material depends on maintenance, quality of installation, use, and climate conditions.  So, use the averages only as a general guide.

To see the full (pdf) report click on the following link:

http://www.nahb.org/fileUpload_details.aspx?contentID=72475