TiVO allows you to transfer the lifetime subscription to the replacement TiVO.
Odd. They don't normally.
You don't happen to be one of the very early TiVo purchasers, do you? The first lifetime subscription deal was worded differently... when it was later changed TiVo granted a one-time transfer between boxes.
The only other lifetime sub. transfer I've heard of was when TiVo offered lifetime Series1 users a transfer if they upgraded to Series2 through a special they ran. I took advantage of that since I wanted HMO.