I would reckon that if it is so hard to find out how long a bee lives without its head the chances are that you can just be reasonable about it and no-one will know any better.

Reasonably they might live for a little while , but would not be able to fly in any logical fashion as they would have lost their sense of direction. They might well be able to sting though.

If I was reading something in which bees kept going after decapitation by a fairy I would probably find minutes or hours rather than days believable.

Don't know if this helps!