I just ordered two hard drives a 3TB (HITACHI Deskstar H3IK30003272SW (0S03208) 3TB 7200 RPM SATA 6.0Gb/s 3.5") to see if its possible to break the 2.2TB limit and the (Western Digital AV-GP WD20EVDS 2TB 32MB Cache SATA 3.0Gb/s) in case the 3TB doesn't work. I should get them on wednesday. Will report back ASAP. Regards...
It's gonna take you a while to get to 2TBs of content. Make sure you do not set all recordings to "Keep until I delete". When I tried it, and filled mine up, I had content dropping off to make room for other content. This is what you want to watch for. If you get past 2TB (and you really won't know exactly when, the hours are not the only consideration, the content of each program recorded also plays a part in the overall size of the content), and nothing drops off to make room for more content, you will have exceeded the expected limit.
I did feel that when the programs started to drop off my 2TB RAID setup that I could have gone further. How much further, I have no idea. You'll also have to do a lot of rebooting or the HR will slow up very badly.
To make a guesstimate, I'd use 500-550 hours as the 2TB limit. After you reach that point, keep a constant eye on it, when it starts dropping programs off to make room for more programs, you've reached the limit. At that point, count up all the hours and let us know. That's about all the advice I can give you. I really felt that I could have exceeded the 2TBs if I'd had a larger capacity.
By the way, I'm glad it's you that's doing this and not me.