I'm in the process of buying a house that was built in 1960. The appraiser that went in there made an estimate that the house would be structurally sound based on present conditions until 2040. The inspector I hired to review the integrity of the house has placed it at "above average" and concurred that it will be sound for a long time. But of course, there are things we need to do within the next four years or so: new room, regrade the land to have stormwater drain away from the foundation walls, etc. I have no qualms about buying this older home, because I understand that maintenance will be an issue in any home. So I'm not quite buying this whole "design life of 20 or 25 years" crud.