One option is to look for used Tivo boxes w/ existing lifetime subscriptions. Sometimes, you end up w/ the cost of the subscription and $100 to $200 for the box itself, not bad. One option is to buy an old Series 1 or 2 box w/ Lifetime and transfer the lifetime to a new box. Then you have 2 boxes and a lifetime service. However, it's not as useful now w/ the all digital switchover. You'd need to use that older Tivo w/ an external digital tuner. It's doable if you use the IR out on the Tivo.

Here's a good Tivo forum.

http://www.tivocommunity.com/tivo-vb/index.php

Saw a few Tivos w/ lifetime on ebay.