Took phones away for a week and here's what happened
My kids are 7, 10, and 14. Wife and I decided to do a "digital detox week" after winter break because honestly they were zombies. I expected the 14yo to absolutely lose it but he was annoyed the first 2 days and then... just moved on? They actually played together, which hadn't happened in months. Built a fort, played board games, the works. When we gave the phones back, 7yo didn't even care that much. The 14yo went right back to it though lol. But there's something to it I think. Might make it a quarterly thing.
A week is honestly the sweet spot. Long enough to break the habit but not so long they feel punished. Might try this with my 10yo