Speaking as a developer, I'd say you'd need your head read if you can't determine fact from fiction. When I've acted as a PM, I can't recall a single meeting where one of the developers on the project hasn't said something about timeframes or techniques that isn't:
a) Downright incorrect
b) Exaggerated
c) Optimistic
d) A premeditated lie

Unless you can sort the wheat from the chaff you'd be on to a loser