Technically they are being handled every time they are picked up and held by you. So for me, this is a couple of times a day in and out of floor time and I have lap time for around 30mins every evening after floor time
Lap time every couple of days along with lifting them in and out of the cage daily for floor time. Amber has a fit when you try and pick her up, shes happier with all four paws on the ground and a head rub
Mine have walk-in cages, so they don't get handled quite as often. I also have my cuddle piggies who like a smooch and those who simply don't enjoy it and who I only health check once weekly. My piggies' main focus is the group they live in and having a happy piggy life rather than a cuddly pet life, but I take care that they are comfortable enough with being handled to not freak out on vet trips.
How often you want to pick up your piggies is up to you. If you have shy, nervous piggies or those that really don't like human contact, I would recommend to go slowly at first.