If flights run to their schedule there's no problem with stand allocation, problems arrive when you have 744's arriving 45 minutes before schedule (In which case, what's the point in a schedule)?
Oh dear - how simplistic....Show me any reasonable sized airport where most flights run to schedule.
Do you know about the effect on the jetstream on long haul flights which can make flight times vary wildly? This is a problem all over the world, not only on stands but also on handling resources.
Issuing a NOTAM means the crew can contact their ops to see if there is likely to be a problem and then can decide how to tackle it eg by slowing down or taking the delay on the ground.
Must be dozens of stand re-allocations every day as events unfold. It's a characteristic of the business...