Over the last 20 game years (1499-1520, France) I have seen my naval support limit gradually going down from 54 to 42.
There hasn't been much change in my and vassals territory in Europe (I dipplo-annexed the vassals Provence and Savoie during that time).
I did do some colonising in the Caribbean.
More than half of my provinces turned Reformed and Protestant (I did use the edict of Nantes and a religious tolerance NI to minimise the consequences).
Over that same period my land support limit has grown, as well as my income.
Any idea what causes the reduction in naval support limit?
Could it be a general economic deterioration of my vassals?