Yeah, you can play for about an hour a day, but that just makes the game go by at a snail's pace. I had it for the entirety of its release, from launch until probably a year after WotLK came out and I still never reached level 80 on my main.
When I quit I was at 74 I think. I didn't even get to 70 until well after WotLK was released.
It's definitely a lot more rewarding if you pump 3-5 hours a day or more into it. That's the only way you can hope to do instances especially... which are the most fun.