I have 2 that i recently got, they are both 900+ grams, previous owner handle them a good bit and let them roam around her snake room when cleaning etc. So those 2 i have been handling daily for 10-15 mins just so they are getting use to me and ill work them up to longer times if they feel up to it. My babies on the other hand, only handling them when spot cleaning etc, maybe once a week for about 15 mins. They all seem to let me know when they are ready to go back to hiding as they try to go in my shirt, under my arm as im holding them etc.
Think it just comes down to learning each snake individually. If their being flighty, alot of tongue flicking or very little, etc. Some may be very comfortable out for periods of time, some may not.
My 150g lesser loves to be out, he'll slither right out on to my arm and coil around when i open his tub(not atm tho as he's in shed haha).