Crating dogs overnight

Question
I have two 18 month old labs who have grown up together. They have been crated since puppyhood and do well with them. Since about 12 months old they have slept we me in bed but are crated when I leave for work with periods ranging 4-6 hours. They've never had a problem with this. My question is: Can they be left overnight in their crates for a similar duration?

Answer
Dogs who get enough physical activity during the day typically sleep all night long - doesn't matter where they are.  So either your bed, their bed or a crate are all acceptable places.  However, I wouldn't expect them to be happy about being removed from the bedroom at night all of a sudden.  Can you crate them in the room with you?  Can they learn to sleep on their own bed on the floor if you don't want them on the bed anymore?  

Be sure they are both getting enough physical exercise and mental stimulation while you're at home.  Being crated for 18+ hours during a day isn't ideal, but if it's the only way for the dogs and your household stuff to be safe, then it can be a solution.

Hope this answers your question.  If not, please let me know if I can clarify.