Apparently all 3 of the Toshiba TiVo models, the DVD playback only SD-H400, and the DVD burner-featuring RS-TX20 and RS-TX60, have what is called TiVo Basic service which gives you 3 days worth of program listings and that's about it.
"TiVo Basic service is a complimentary version of the TiVo service available only on DVD integrated models from Toshiba and Pioneer. TiVo Basic service is not available on standalone TiVo DVRs.
No activation is necessary to use TiVo Basic features. By upgrading to TiVo Plus service, you will be able to use the additional features listed in the table below:"
So you should have a sort of lifetime subscription on that machine already, but you'll have to contact TiVo Customer Service and give them the TiVo Service Number (look on back near where power cord enters), or TSN, for them to check to see if the account has ever been upgraded beyond that, and whether the upgrade was a by the month or year or 3 year deal, or lifetime.
Or you could just let it "phone home" and see what happens. You'd still have the TiVo Basic service.
That "lifetime" service, by the way, is for the lifetime of the unit itself, not the unit's owner.
We know some lifetime extension tricks and techiques around here if/when that Toshiba breaks down on you, so hang around, read old threads, learn stuff.