... is something that you should avoid, obviously. Don't be that busy speaker who delivers a mediocre presentation because you didn't have the time to prepare properly. At least that's the advice for speaking at regular conferences and similar events. You should have had enough advance warning; not using that time is usually your own fault - be it due to bad time management or over-commitment.
In some circumstances, however, having to prepare a presentation on short notice is almost the norm; in business environments, for example.
