If the 2TB internal drive fails, and it probably will, think about going with an external drive that's not a 2 1/2 inch drive. Plenty of threads here on how to roll you own. Or, if you're lazy like me, Weaknees has a nice, easy to install kit with everything you need.I purchased a non-lifetime Bolt on eBay and changed out the hard drive when my bolt died earlier this year.
I wanted the 3tb 6 tuner version unit for the storage. It had died the year before and I purchased a WD 2TB drive but it didn't last a full year.
Only issue I had was the new hard drive had the version 4 installed. Took some doing (and I don't remember what I did) but I finally got my version 3 back.
I read that they tend to overheat so I bought a laptop fan and put it under the unit after replacing the hard drive. Jury is still out on whether that works.
There are also plenty of threads here on how to upgrade your Tivo from TE4 to TE3. Lots of us here prefer TE3 like you do.