Naah you pick a record threshold by policy. The streams are so tidy at this point that with motion detection you can pack months on very little space. I've allowed my surveillance station to fill up 1TB, no more, and with nine 720P or better cameras, being constantly triggered by headlights and stuff, I can still go back about eight weeks.
Thing you gotta keep in mind is if it was built in the past twenty years, and it was worth surveilling, there were tape decks. Their archives were thin. But when those tape decks went away, the RAID arrays came in and they're phat.
If I dedicated my 40TB home NAS to recording the cameras I got I could do 24-7 recording of 9 streams at 18 frames for a month before I recycled anything and a 40TB array is Amazon Prime territory.