Pluto's orbital period is 248 earth-years. That means from the time it was discovered (in 1930) until now, it hasn't accomplished even one revolution around the sun.
Two relevant thoughts from the Reddit thread:
"...assuming they have the same life span as humans, Plutonians would never celebrate their Plutonian birthday!"Image via Thinking Sci-Fi.
"I wonder when Plutonians celebrate their New Year, and how much more awesome the parties must be if you have to wait that long."