Heinlein is great reading for when you're 14 years old.
After that, PKD in your late teens and KV in your 20s.
Mark Twain is for pre-sci fi and re-read again when beyond sci-fi.
Voltaire is probably too much for you guys, but I'd say in your 30s, if you've exhausted RH, PKD, and KV.
Heinlein at an advanced age is sort of silly. Something a marine might think is literary.
(Not disparaging marines, marines are an important part of the Navy!)
#11 | Posted by LampLighter
>their prior customer base doesn't have enough money to feed their families
-Uh, they never did? Hence they up?