how long in the crate during the day is too long???

hi guys. our puppies trainer told us we need to leave him in the crate longer than he’s out of it during the day (to get him to be used to it) and i just feel like it’s so excessive ?? I feel horrible at the thought of him spending more than half his day in there. Is this a normal training thing or should I not trust it? our puppy is 6 months old