In general, it is a good idea to wait on adding the wire numbers to a project until it is done. Of course, this isn't always possible, but it will simplify things to wait as long as possible. Once you add wire numbers to a project, the software will begin error checking on those wire segments. So if you still have circuitry changes to make, you will then be prompted with messages asking you about short circuits or duplicated potentials being created as you move things around. This will mean more messages for you to acknowledge as you work. So saving wire numbering until the circuit is done will save you steps.
Wiring Manager
Automatic Wire Number