Well, the 70 lbs. limit may also be related to the maximum amount of cargo an aircraft can hold, and how that relates to each individual passenger.
But, otherwise, just use common sense.
If, by chance you're flying Delta (as we are), this may be of some use to you:
http://www.delta.com/cwswaittime/tra...time/index.jsp
Orlando Int'l Airport's code is MCO. You're own your own for local airports. I'd probably expect it to take a bit longer than what's posted, but I have no real clue as to how accurate their numbers are.
I don't know if other airlines have anything similar on their websites.
Finally, I'd heard that they make you turn on any suspicious electronic equipment to prove that it is what you say it is.