Depends on the type of project. If your service is down, you can schedule some maintenance, fix whatever needs fixing and come back up after few hours.
But if your service is large enough, a maintenance window costs you money, reputation, customer satisfaction and makes you breach contracts and service level agreements... you may want to find ways to minimize maintenance downtime.
In that case you will want to make your code straightforward enough so mean time to detection and mean time to repair is low by emphasizing maintainability, namely, clean code with accompanying tests.