Terbinator
As you mentioned it comes down to peoples perception. I just don't see why you would have up to 1TB (or more) of programs anyway, surely once you've seen your episode of Corrie there's no need to archive it.
As burble said, one reason is people away for periods, be it for work or just holiday. Another is for people like me. I go for days at a time without watching much more than TV news and maybe newsnight. But periodically, I've have a lazy “catchup” day. Also, I don't like watching a series over the course of several months, so I record a set of programs, then watch them in one sitting, or several lengthy ones. For instance, I watch all four (or five, whatever it was) series of The Wire by watching 3 or 4 per night, most nights. Right now, doing anything like that means burning them to CD until I'm ready, and then when I'm done, I've a load of useless CDs.
A 1TB drive might not completely eliminate that, but it'd sure cut it down. For instance, we recorded Silent Witness and the three-part Above Suspicion" recently, and the latter sat there for several weeks until the wife and I were both available and in the mood to watch it. Above Suspicion
alone took about 10% of available drive space, and it's only three parts.
If you just watch Corrie and Eastenders, and keep fairly up to date, then current drive sizes are probably OK. But if you keep a few documentaries, and a series or two, and a handful of thrillers, all until the weekend or a suitable time, you can run out easily.
Oh, and with the current machine, I don't like letting free space get below about 30% at worst, because that seems to be when problems requiring a reset (deleting all content) start to appear. So, I start with 160GB (standard Sky + box, but the 320GB HD have the same issue, just not as badly) of HDD. 80GB is reserved for “Anytime”, despite disabling it. That leaves 80GB for me to use. Of that 80GB, I don't want to drop below about 70% use, meaning I actually have something like 55-60GB for programs.
Not much, is it?
With the HD boxes, about 140GB is reserved, leaving 180GB, leaving you about 125GB of usable space if you keep 30% free … and HD recordings take more space anyway.