Trouble is, these days there's usually 2 heats of "A" and 2 heats of "D". That makes at least seven in total. With the usual 10:00 start, if you run 20 minute heats plus 10 minutes between, it's at least half past one before all the first heats are done. Even with no lunch break, and not allowing for any stoppages, delays etc it would be at least a five o'clock finish - assuming that none of the other classes run to two heats.
Mind you, it looks like we might need to run a "DM" class this year - just for Makaras......
Ian