On the contrary, generally the eggs would have been laid during the last 2 weeks and in probably another week or so the eggs will hatch. And the chicks will be in the nest for another month before they are ready to fly north. So all in all mid to end July will be time for them to go.
Anyway as the saying goes a swallow doesn't make a summer.
If you observe more , the bee-eaters like to go back to their favourite perch if they are not disturbed. If you can hide behind a blind would be even better.
They tend be more active during first light and by late morning, you can hardly find them.