When maintenance licenses licenses expire on Avalanche 5.3 - 6.1, your production units will not have any change in behavior. Registered Maintenance licenses are required when an older Avalanche Server hosts devices with newer enablers.
IE: Avalanche 5.0 Server and Devices with a 5.3 Enabler. These devices require both, a Maintenance and a Base license.
Avalanche Servers on 5.3 and higher do not have this need, since ruggedized devices do not have an enabler higher than 5.3.x