Does the age of an actor matter?

So there was a discussion on a Facebook event invite about the age of one of the actresses in the upcoming production of Mercy Seat at the Strand.

It's a interesting question for directors (and I think for actors too), what's the balance between talent and someone fitting the description of the character?

My initial thought is that it doesn't matter that much as long as the actor can portray the character. (Though this next comment might come off as a little ageist, please don't take it that way...) My second thought is that it is easier for an audience to believe a younger actor as a character that is older, than an older actor playing someone obviously younger. Maybe this view is derived from the fact that when I act I usually play an older character (I really rock at the 60 year-old ladies if I do say so myself), but it drives me CRAZY when and actor is cast in a role that they are obviously too old for.

The first example of this I can think of was Spot's version of Hamlet. Hamlet is supposed to be younger, somewhere under 20, and Ophelia the same. Though Michael Leicht and Jen Mikulski are both very capable actors, it drove me nuts that they looked late 20's/early 30's.

So what do you think? Is talent more important than age or do they need to balance each other?