The average load of a good massager is not more than 3 hours of use, which is a good average, because in no case should you spend all the time using the massager on your body. There are devices that use conventional alkaline batteries, but they usually last less than two hours.
It is always advisable to invest in devices whose batteries can be recharged using a charger. Good quality massagers can last a lifetime, while others have a lifespan of 5 to 10 years. It depends on the brand and the care with which you treat it.