If something were ever to happen, and you have receipts that prove you bought gas and paid for hotels, to park fees in multiple locations then that would show you are just passing through. The states would have a hard time regulating interstate travel as it is the preview of congress. It all boils down to what is your intent. Are you moving to the state in question? Just passing trough? Or on vacation and will be around for a few days? It depends my brother.
My advice would be ensure you have your letter in hand, follow a pre arranged plan, try to reserve when it makes sense, keep all receipts (lodging, gas, restaurants) to show your intent. Passing through is completely different then moving to or staying for a few days.