Longest Production Runs

Lincoln Wheat cent - 1909-1958 - 50 years
Lincoln Memorial cent - 1959-2008 - 50 years
Jefferson nickel - 1938-2003, 2007-2008 - 68 years
Roosevelt dime - 1946-2008 - 63 years
Washington quarter - 1932-1974, 1977-1998 - 64 years


Besides the metal change for WW2 and the new designs from 2004-2006, the US Nickel holds the records I think

Longest run of a one sided design would be the Lincoln Cent obverse at 100 years

***edited math

Gotta love the Swiss

a good majority of their coins haven't changed since the late 1870's

Actually my math was flawed. I subtracted 1909 from 2008 and it equals 99. Technically if you include all the years it's 100. You also have to add 1 year to the equation of each one

I disagree, should be 66 years. Since Jefferson's image changed in 2007, I count it as a new design.

The Swiss "silver" coins changed design slightly; a 22nd star was added when Switzerland gained an extra canton in 1979.

The oldest unchanged designs are the 5, 10 and 20 rappen, commencing in 1879, 1885 and 1881 respectively, and still being issued today. Switzerland is of course a much smaller economy than the US, so not every denomination was struck in every year, but they're frequent enough to still consider them a continuous series.

If I am not wrong, I think the Dutch ducat has been running over 400 years and is still struck today with similar elements. Technology helped changed over how the coin appearance looks like but I think the gold content still remains the same.

D'Oh!

Okay, what I said above then should read "I disagree, should be 66 years. Since Jefferson's image changed in 2006, I count it as a new design"

So to summarize...

1938 - 2003 -- 66 years -- one design for each obverse and reverse.
2004 - 2005 -- two years -- two obverse designs, four reverse designs.
2006 - date -- original reverse resumed, but new obverse.