In the sense that nothing in the story really dates it, or that there's some sort of idea or approach in Maus that no longer holds up. I read it several years after it came out, and it was just fine. A lot of people might have gone ga-ga over Maus simply because it was a comic book tackling a 'serious' issue... pretty much still a novelty in 1986. But even now, when 'serious comics' are old hat, Maus still has a pretty good story to tell, I think.

Now it's true that at one time it may have been the benchmark for graphic novels, and it has since been surpassed... but I dunno if that's exactly the same thing as it "not aging well". That's just natural evolution in the medium.

And as young as graphic novels are, who knows what we'll think of stuff like 'Blankets' and 'Jimmy Corrigan' in the next 20-30 years?