Regatta capacity

A Marshall's thread led onto people discussing the fact that many
regattas at this time of year are full or nearly full; this is in sharp
contrast to a number of regattas at other times of year being cancelled
due to lack of entries, Docklands for instance.

Why is this? is it:

Location, time of year or the anticipated level of competition.

If it's time of year then is this due to the training profiles of the
crews ensuring that they peak at certain events?

Is it all of the above?

Roger

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