Like Dan said... if you don't have a residence in the state you get a plate from, it's just not legal. Your buddy's address doesn't qualify. PO Boxes don't qualify. And even if you lie and get a plate... here is why it just doesn't work.
You get a Nev plate on your CA dirt bike. You think you beat the system. Two scenarios exist:
1) If you never get stopped by LEO you never needed it in the first place.
2) If you do get stopped by LEO your CA ID and out of state plate is an immediate ticket requiring you to get a CA plate which will never happen... so again, you never needed the out of state plate in the first place cause it did you no good.
The out of state plate is a FALSE sense of security.
I've had guys say "Oh they'll never catch me !" If thats the answer why did he need the plate. Might as well have been trucking down the highway with a Red Sticker.
I've had guys say "I don't go to Gorman so my plate never gets scrutinized !" or "I only ride desert... no one will ever see me." OK, again, what was the value of getting the out of state plate if it can never be scrutinized or seen ?
Take it a step further... you get into an accident in CA... you will get a ticket for no CA registration... the insurance company also denies your claim cause you participated in registration fraud. If you were at fault in the accident you get to fix that guys Mercedes with your own CASH !
What if you LIED some more and get a DL from the other state too so you can pass that road side stop ? Now you gotta lie a bunch more and register all your CA cars in the other state and insure them there cause you no longer have a CA DL. Then you run the risk of any insurance claim being denied if you wreck in CA.
If you truly have a home in another state... plate away !