I know why water beading doesn’t get old even though it isn’t the “end all” indicator as to whether or not a wood deck is in need of maintenance. It is however safe to say that if water is beading on your deck, there is likely plenty of product protecting the boards.
These photos are of identical nature, taken one after the other, at 3pm in the shade. They help explain a thing or three which likely answers many questions. Hopefully yours too.
Where you see water beading means that those boards have been washed and stained AND the stain is dry. Where you see water that has penetrated the wood means that those boards have been washed only. It’s safe(enough) to say that the stained boards don’t look all that much different than the wet boards.(And for the record, the “wet” boards are really only damp, certainly not soaked.)