I watched 24 in 2001 but only ever saw season 1. I just re-watched all of season 1 in one day. Total runtime is 17h20m so it is possible by making an early start. There's a lot with which you could criticise 24 but - like a blockbuster movie - park your brain, go with the flow and it's great entertainment.

Some people say 24 raised the bar for TV shows. My memory is that it was one of several shows from that era which collectively raised the bar: The Sopranos, Band of Brothers, Six Feet Under, The Wire, The Shield. Those shows may be held in higher regard than 24 but none are as relentlessly gripping.

Warning: An entire season of 24 in a single day can mess with your head.