I recently upgraded from a 2-tuner Premiere to a 6-tuner Roamio. I recall that on the Premiere, if I used the "last" button to toggle between two channels, and nothing was recording, it would use one tuner per channel, and I'd have the full 30 minute buffer for each. But with the Roamio, "last" reuses the same tuner, so I lose the buffer each time I switch. Is this normal? With 6 tuners and nothing recording, I would expect to be able to go back to any of my last 5 channels and have a buffer available.