He also says that watching them in a rush all the seasons blur together. Mmm... I kinda know what he means, having done that for some shows via DVD.
Maybe if you did that to standalone centric shows like The X-Files, or TNG, the Simpsons, etc, I could see how it would be hard to think of an episode and try and remember what exact season it was from.
However I always felt that was a cool thing with Buffy & Angel, that each season always had a distinctive feel. Helped by the cast changes a lot, but also by the Big Bads, esp with Buffy.
eg. when I think of Buffy Season 3 I think of the Mayor & Faith, Season 5- Glory, Season 4- Adam, etc.
Angel is fairly easy too, seasons 1 & 5 are so different in look to the others, Season 4 was very arc heavy with the Beast/Jasmine/Faith stuff, I guess s2 & 3 could blur a bit with all the Wolfram & Hart stuff, but even that... Lindsey & Darla- season 2, Holtz & Connor- season 3