From this website:
Bumblebee colony development (Stage2 of the yearly life cycle)

"Most workers return to the nest every night, but some may spend the night outside sheltering under flowers as the males do. This can happen if there is a sudden change of weather in the evening and the bumblebee becomes stranded outside. "

"Males do not return to the nest once they have left it, so spend their nights either inside or hanging under flower heads. In the morning they are often very lethargic and may appear to be ill, but this is normal. They just need to get up heat by drinking nectar or being warmed by the sun or both. "

But also - the average lifespan of a worker is only about 40 days.