Grace GBS3500 banknote value counters require regular maintenance to ensure accuracy and longevity. Routine maintenance tasks include cleaning the sensors and feed rollers, checking for any signs of wear or damage, and calibrating the machine if necessary. It is important to follow the manufacturer's recommended maintenance schedule and use only authorized replacement parts to avoid voiding the warranty or compromising the machine's accuracy. Proper maintenance can extend the lifespan of the machine and ensure accurate and reliable counting of banknotes.