This is a big loss of money, so do think it through. I am a big proponent of paying taxes, but this is just impractical.
Here is the legalese (I am not a lawyer, so please treat this as what I understand and follow).
1. You are required to move your vehicle registration up to 1 year after you have moved. However what constitutes a move, and when the clock starts is not only ambiguous, but also not explicit.
2. When you make the move, the road tax is to be collected back from the original state, pro-rated; and they have no incentive to give you the money. I know of only 1 case out of hundreds, where the refund went through, and that was after 8 years, with no interest.
So if you want to be on the right side of the law, I make sure that I have one trip where the vehicle has entered from outside the state, at least once a year and keep a record of it. I did this with toll receipts, which is now easier with FasTag.
As far as the law is concerned, I am just visiting and have no intention of moving the car/bike.
I know >>100 cars that are in my society complex, that are out of state reg. This is in Bangalore. I have know similar numbers in Mumbai and Delhi. If the cops want to harass you they can of course. But the high court in Karnataka gave them a nice dressing down the last time they had organised a ruckus about this, 4 years ago. I myself have used an MH car in KA for a years. And 80% of my friends have out of state vehicles in Bangalore. The only ones that have local reg ones, are the ones who bought a car here.
On a more evangelical note, one nation, one tax, one registration method needs to be desperately put in place to break the RTO mafia. Don't bend over backwards for them and waste money.