I've been over 150 in a 30 before years ago and I know it was fucking stupid. I like to drive fast but only because I like it. I never rush to anywhere as your better of late than dead. I always slow down for kids and animals or too many cars etc.
It depends. Here we have roads that are posted 45 but then suddenly go to 35 and then back to 45. I discovered my short street is a 45 mph zone. Some streets that seem like they should be 45 are 35. I try to maintain the right speed limit but it is another one of those complicated issues especially here.