Screen time battles are exhausting

I feel like I'm constantly fighting with my kids about their tablets. My wife says I'm too strict, I think she's too loose. 9 year old is sneaking screen time, 11 year old thinks 2 hours a day isn't enough. We set limits but then one of us cracks when they're bored or driving us crazy. Anyone have a system that actually works or am I just supposed to accept this is going to be a constant thing?