I’d say a used/older car should be checked out by your regular mechanic at least once a year. The reason is that oil should be changed each year (even if the car isn’t used much) for the health of the car. You can use that opportunity to ask the shop to do a check on the car for safety. No need to go to the Toyota dealer though, go to an independent shop that can scan codes properly and has worked on lots of Priuses. For that oil change visit, I’d recommend going to the same shop, not asking at a local ‘Jiffy Lube’/while-you-wait oil change place or a large chain, as those companies will probably tell you you need things that you don’t need.