CA- registering out of state bike <7500mi

I'm looking at a bike with 4500 miles on it registered out of state (i'm in california)

The current owner says it will be expensive (double) to register it in CA before it hits 7500 miles.

My question is this: If I purchase this bike, do bank or insurance companies have any particular interest in having it registered in the state? or should I be ok to ride it for 3k miles before I register it. (if the police don't decide to make me correct it anyway)