Maintaining the kids' interest in being read aloud to as they grow older is something I've been working away at. I'm of a mind to think that the key is to treat reading aloud as something families do, rather than something parents do for children who can't yet read (at least at that level) on their own. In other words, I think that if you create a culture of reading aloud in your family, one where adults read to adults and kids read to adults (for mutual pleasure, NOT for evaluative purposes) and adults read to kids, then children will be less likely to abandon the ritual as they grow in maturity and age. They won't see it as something that "little kids get from their parents when they can't read to themselves yet", but something that "human beings often enjoy doing together".
So I try to include Chuck in our readalouds with from time to time. Often that's tough, as our 'down-time' and bedtime schedules rarely coincide with his. But I'll sometimes save an interesting magazine article to read at supper time. Or we'll share a favourite audiobook with him (perhaps not necessarily at the same time, but we at least share a common exposure that way). And when we're on vacation we always all listen to the readalouds. Chuck and I used to, before kids, read aloud to each other on long car trips, and we share this with the kids.
Two message boards I'm a part of recently had polls asking how often parents read aloud to their kids at bedtime. On one general parenting board 53% said "never". On another over 90% claimed to read aloud to their kids "with some regularity" and this was a poll concerning kids who were already reading independently. The latter was an education-focused board for parents of gifted children. Stark contrast, hmmm? I wonder which direction the causality runs?
I think that reading aloud to independent readers is very important. It allows you to share a common body of knowledge and vicarious experience with your children, to pass along your own love of certain books and favourite authors, to spend time being with your children, to expose them to themes and subject matter that they might not choose to read on their own, and to 'read a little over their heads', expanding their comprehension and vocabulary far more than will happen just through independent reading. Two of my kids were reading independently at 4, and I just never would have entertained the thought of giving up reading aloud at that age... thankfully that early start got us all over the hump of believing that reading aloud is just a helpful thing parents do before their kids can read independently.
I know that families with children in school have a tougher job finding time for reading aloud, and I can't presume to truly understand the challenges of scheduling and time constraints facing families with kids in school. I can't help but wonder though whether, while it's presumably more challenging to find the time, it's perhaps even more important that they do, because relative to families that don't do school they have so little shared experience and so little shared time. Reading independently, though important, does not fill that void.
At the risk of appearing dishwasher-obsessed, I will mention that hand-washing dishes as a family creates a wonderful opportunity for shared reading aloud. One person can be appointed the reader-aloud, while the others wash/rinse/dry/put away the dishes.
Jim Trelease's "Read-Aloud Handbook" contains some very compelling arguments and statistics about the importance of reading aloud as a family. The read-aloud bibliography is also great. Highly recommended.