Should services be turned off prior to performing updates? Let's say you want to upgrade your OS X server from Yosemite 10.10.1 to 10.10.2. Should you turn off OS X Server services prior to the upgrade?

Should you also turn off when upgrading from Server.app 4.0 to 4.1?

I can't seem to find any Apple documentation that suggests to do it but then again, Apple documentation seems limited in a lot of regards.
Most likely an upgrade like that will behave like Java updates do in macs. It will replace the software in the background and won't start using the new software until you restart the program. 

In terms of best practices, I would say go ahead and update it with services still running and as soon as it's done, restart the machine to give it a fresh run.