First of all, they state clearly that a "lifetime" subscription is for the life of the unit, not your lifetime, so if you buy another you'll have to buy another subscription. That having been said, TiVOs can be repaired and can even be "improved" (check out
www.tivocommunity.com or
www.digitalrecorder.tv for example), and I personally think that the odds of the unit completely dying before you've saved money by buying the lifetime subscription instead of the monthly are slim to none.