An old Python record won't seem as comically old-fashioned, therefore, as a video of the TV show. The more I think about this, the more it seems true. A good test case is old Peter Cook and Dudley Moore records. But watch a tape of the TV show and you'll be brought up cold by the early 1960s attire and, more to the point, the fact that they're in black and white. You can't help interpreting them as something from then, whereas listening to the records it's easy to forget that they aren't from now.
Comedy albums are, sadly, out of fashion nowadays.
But as far as longevity of humour goes, this is a case where less is more. The parrot sketch will sound fresh for decades, but watching it you won't be able to stop noticing John Cleese's sideburns.