I will probably keep my AM21 hooked-up until it dies or they completely stop software for it. One thing that I have personally stopped doing is filling in missing subchannels with incorrect data. It was fun for awhile but I just get frustrated with the clutter of incorrectness. I just leave my home zip and the one zip that fills in MeTV for me with correct data. I just don't watch the subchannels much, and those I do are MeTV, Create, and MHz Worldview, which all have correct guide data.
The clutter of incorrectness can also mess up the AM21 and cause the need to reset it. For me, all I have ever had to do to make the OTA channels disappear off the guide is disconnect the USB and RBR and it's like you never had the AM21. It should go from "Sat & Antenna" to "Satellite" on the menu/settings screen.