Back when the episode first aired there was a 19-month gap between the airing of the first season's finale (episode 124) the second seasons finale (episode 224).
It took 345 months from conclusion of Season 1 to the release of the complete first season appeared on DVD.
If season 2 was released today (which I know it isn't) it would only be a 342 month gap from the conclusion of season 2 and its DVD debut. So to be fair, it wouldn't be until after February 2007 that the release gap from season 1 to season 2 would be a disproportional spacing. So having it come out in spring (March/April 2007) is a reasonable release (only about a month or two longer than audiences in 1978 had to wait after watching season one to see the complete second season).