With the film as precedent, actual age doesn't matter, as long as the actor can act the part. Makeup is a beautiful thing.
That said, I loved the Colleen Dewhurst/Ben Gazzara Broadway production, directed by Albee. They were similar in age to Morton and Letts.
Woolf is my favorite modern play, and with each production I find it fascinating to see what the actors bring to the table. Do they emphasize the love story, is there true hope at the end, do they bring the humor? Or not?
I'm very curious what Flockhart and Quinto do with these characters.
Letts is my all-time favorite George, he just wowed me with the depth he brought to the role. I was interested in what Eddie Izzard's take would be. Rupert Everett, not so much.
I'd love to see what J. Smith-Cameron could do with Martha.