I just wanted to note that today is Ian McDiarmid’s birthday. (Forgot his age, sorry.) Huzzah!
I believe the Dark Lord is 55.
Of course, he is a clone of the first Ian McDiarmid, who appeared in ROTJ at the age of 135. Nevertheless, all McDiarmids are masters of both the Dark Side and being sublimely creepy.
Here’s to another 55 and a clone after that!
<sings>Happy Birth-day, to you…Happy Birth-day to yooooo, Happy Birth-day, dear fountainofallthatisevilandcorruptinourgal-ax-eeeeeeee, Happy Birthday tooooo yooooooou! </sings> 
I think it was darn clever of Lucas to hire someone who was 36 years old (as Ian was in 1983, when RoTJ was made) and put him in age make-up so he could play someone old – all with the idea that he would play a younger version of himself (Senator P) in the prequels.
NTBUSWAB (Not To Bring Up Star Wars Again, But) via The Onion