well i would keep them because i think there gonna raise in value also the government is thinking of starting to make the Penny and nickel out of steel because of the price.......... but if your gonna keep them you might as well keep the pre 1980 pennies
hope someone else can answer your other questions...........................
People keep pre-60 (I keep pre-70) simply due to their rarity. I would suggest keeping at most a roll of each variety, unless you are speculating on the future value of Nickel and are hoping the government will remove it's ban on melting lower denom coins.