Strictly speaking it is not true that you need to have your car serviced by a Toyota dealer in order to maintain the warranty, at least not for the first three years. If you choose to have it serviced elsewhere you must abide by the manufacturer's recommended service intervals and use genuine Toyota parts or parts that match OEM quality. Once the standard warranty period has passed, you can qualify for an extended warranty if you have your servicing carried out at a Toyota dealer, and this will apply every year it is serviced by a Toyota dealer up to ten years or 100,000 miles, whichever comes first. You can read about this in detail here - mag.toyota.co.uk/toyota-warranty-how-it-works/