Fourty plus segment here, work in a group where the average age is actually mid-30s despite a couple of junior people. Some of us are generalists, some specialists, all have kept abreast of assorted technologies as our careers have progressed.
The narrowest experience is actually amongst the mid/late 20 somethings in our group. I'm not sure if it is that lack of systems experience, not much exposure to C and lower level languages, or what, but they need more mentoring than what I recall needing at the same age.
I'm currently doing that for a couple of them and it is actually both challenging and interesting. Challenging mainly in how to convey tasks, teach them troubleshooting (without the hand holding), and a few other items. Interesting because we all learn differently and seeing how others approach problems either reminds me of my own trials or forces me to think out of the box on how to explain things.
Personally, I've always been a bit of a control freak when it comes to development -- I want to know system level through whatever level I am developing at. This often includes system administration, database management, etc. This has become much more challenging as new technologies come about -- so in those cases, say NoSQL, I will focus on one or two solutions rather than trying to understand each. Build a basis for the concepts, where it is useful, and then test, collect data and reevaluate.