Honestly, this depends on the scope and nature of your event.
We advise you to start putting plans in place as early as possible (as soon as you know your event would hold).
Eventigo advises engaging the services of an event planner early in the planning phase to allow adequate time to plan, prepare back up plans and get everything in plan.
However, we entertain last minute requests as we have had clients book our service as late as 3 days before their event. Yes, we delivered on the job (smile)