Is the Agent Pool Maintenance script customizable?

Question

For our largest pool, 500-700 virtual machines, we have enabled the Maintenance Job.

Are we able to edit this maintenance script that we enabled?

We have noticed that machines with an uptime of more than 60 days start having Agent / Azure Task failures that cause failures in builds until the virtual machine is rebooted. We would like to add an uptime check to the maintenance job's script and reboot machines as part of this operation.