Saw a mate today for his 25th who i havent seen for a few years. His younger brother and mates have nerf guns and not only mod the springs and batteries to increase power and firing rate but add red dot scops and laser sights. Cant wait til i have a few kids and get into it myself.
IVY_MiKe, quick mod and it then takes 4 AAs and boosts the power of the motor to boot. Then add a stronger spring, remove some air restrictors and you are good to go with twice the distance and twice the rate of fire.
As for the age question, i'm 32 and i see no problem with playing with toys if you want. Getting older and mature does not mean you have to stop doing the things you loved doing as a kid. I work all week, i own a house and car, i have a girlfriend.... I'm a very creative person and need outlets to be creative. Modifying something like this is a quick/cheap/easy outlet. Certainly a lot more simple than my other project of the Coil Gun. :)