My cat sitter told me that as the kitties get older, they are more stressed out over their owners' absences, which I translated into - as they get older they miss you more.

I've really noticed this with Peanut lately. Even when we're gone just overnight, she is really clingy for a day or two, then she's back to her old stand-offish self. She used to be stand-offish all the time, but now seems to really miss us. We were gone over the holiday weekend and this morning Terry had to head out of town, so poor little Peanut was yowling for us and I hadn't even left yet!

So like somebody else mentioned, enjoy it while you can because he'll be back to his old ways soon enough...until you go away again.