As I understand it, lifetime service is good for the lifetime of that specific serial number TiVo box. When the box dies the lifetime service dies (unless the box is still under warranty). Fortunately, the most common failure is the power supply, which is affordable and easy to replace. HDMI ports fail but the analog outputs usually still work and there are even cheap RGB/audio to HDMI converters. Beyond that, Weakknees might be able to fix a bad box and retain the lifetime service.
Kmttg is a wonderful tool to automatically copy unprotected TiVo shows to your computer. BUT if the show is marked as protected by your cable company (e.g. pay channels) you cannot copy the show, at least not with kmttg or any method I know. Kmttg can be configured to automatically transcode files from the native MPG2 format to many other formats. I use h264 encoding in an MP4 container and compress show files to about 10% the original size (with some loss of resolution, of course).
I have one TiVo in another building and I use kmttg to set channels, season passes, etc. as well as download, all remotely from my PC.
I used pyTivo in the past. But now I store shows on my Synology NAS (which is always on) and play them on my TV using FireStick or Roku. Both of these are MUCH faster than TiVo's internet streaming interface and I can use one remote control for everything except actual TiVo replay. The current Fire remote (which is not expensive) has volume/mute as well as on-off for TV and video receiver, plus voice search for streaming content.
Also, a Roamio pro and plus are the same except for hard drive size. You can "upgrade" either to much larger hard drives using instructions on this web site
. My Roamio plus has a 10T drive and it works fine. The upgrade is fast and easy unless you want to save recorded shows, which requires many hours to copy shows to the new hard drive. The Roamio will automatically configure a blank hard drive up to 3T but you also need a computer and free software to enable all the space on a larger drive.