Signal travel time isn't really a significant delay in the planning cycle. What matters is waiting for orbiters to fly overhead for downlink, DSN scheduling, and the 6 to 8 hours it takes to write a typically 1 to 4 sol plan (set of commands). Also constraints of getting it done during regular work hours, ish.
I should say, the above response is with respect to ops for landed Mars missions, during the surface phase. I haven't been involved with ops for missions in deep space orbit or coast (& Entry Descent and Landing), lunar missions, etc. in which more of a real-time-ish paradigm is possible, so I don't know how that works.
