When Bridget DeZiel's hot tub turned cold earlier this fall, she figured the lifetime warranty meant she would get a new heater gratis. Yet the Bloomington woman paid $250 to replace the unit because she was told that "lifetime" on her eight-year-old Cal Spas hot tub meant seven years.

The definition of lifetime is slippery when it comes to product warranties. Manufacturers often mean the expected lifespan of the product, or they could mean the time it's owned by its original buyer, according to the Federal Trade Commission. The least common usage is the lifetime of the owner, the FTC says.

In DeZiel's case, the dealer made a mistake, because lifetime really meant lifetime and DeZiel should have paid only the labor cost, according to Cal Spas spokeswoman Courtney Salas. The Pomona, Calif.-based company has contacted its Minnesota distributors to correct these misinterpretations, Salas said.

As for DeZiel's overpayment, "we'll take care of it," Salas said.

What surprises have you encountered with lifetime warranties?