hmmm, well im not sure i have much advice that would be helpful on this subject, but i dont think its stupid or silly or shallow at all. i for one like knowing whats up in a relationship, and almost 4 years....thats wow for just dating.
on one hand, you do know that he wouldnt have been with you this long if he wasnt absolutely into you, but then again, everything in this world is uncertain, and you just want him to let you know that he is looking for something more than just dating.....
totally understandable, i like knowing a guy is into me and not some other girl....
but i know its something you want him to do on his own, because if its forced, then it might not necessarily mean what it should mean.
i would think of hinting something to one of his friends that might be willing to hint to him for you (without saying it was coming from you)...
like saying "dude, you have a great girlfriend....and youve been together for what, 4 years now? have you thought about maybe something more serious? like maybe a promise ring?"
i dunno just something along those lines.
i hope my suggestions have been helpful. like i said, im not too experienced with guys...and the only guys i ever seem to date dont express themselves much...*shrug* but i really hope the best for you
good luck and let us know what happens