Personally I love talking with people older than me. Most all the friends Ive had were people older than me.
Jw or not I think having older friends is good advice.
I know having had younger friends I felt younger. lol
Having older friends made me realize, they to, went through a lot of the same stuff I had.
At the end of the day age is really a number. I have met 60 year olds that were as immature as a teen. (but not in a good way) I have met younger folks that were more mature than someone twice there age.
Having older friends is not just a jw taught thing, its a human connection thing.
Jws do mix basic psychology, with there teachings. Its one of the 'hooks' as they bundle it up with crap.
Also I wanted to add that young people do need to have others around there age to chat with. But when you hit around 30+ that might change a bit.