OK, talked to Tivo cust service chat, and they replied:
" The TiVo device is yours and you can sell them if you would like to. If they have Product Lifetime Service that would go with the TiVo device with the new owner. "
30-day money back guarantee should apply to tivo & lifetime as well.
Just strange I haven't seen any for sale on ebay etc... maybe everyone so happy they don't want to part with them