The Great Pyrenees dog breed will shed quite a bit all year long so you need to be prepared for cleaning up dog hair constantly from the Great Pyrenees.
Make sure you groom the Great Pyrenees dog often to prevent hair from getting all over the place but even then you're gonna get some dog hair on things that you'll need to clean up.
It can vary from dog to dog but what I remember when I had a Great Pyrenees during childhood the Great Pyrenees tended to shed a lot more during the winter than they did during the summertime.
But as long as you groom and brush the Great Pyrenees dogs coat there should not be much shedding on furniture, carpet etc.
That's the key is to constantly groom the Great Pyrenees to prevent getting dog hair everywhere.
They are great dogs as well though so they are worth the work involved.