At first I did, growing up in the 60s and 70s. Everyone seemed to, so as I child I remember thinking "they can't all be wrong." The 1975 mess didn't throw me off too much, because I thought that if we didn't know they day and hour, how could we be so sure 1975 was the year.
But later - I started to realize that the natural world just doesn't work that way. Why does everything else exist, live, and then die (or be replaced, as in nature) but humans would be on this recycling program of sorts. What makes us so special? It didn't make sense. Also, I began to realize that people are followers, and if they want something bad enough they'll do whatever mental gymnastics it takes to keep their belief going.
I agree with undercover, once I starting doubting all the beliefs just became ridiculous. I regret not doing a lot of things while I was younger, so to be honest I am trying to play catch up. It is a harsh realization to know you could die at any time, but it makes you want to really live in the now.