Last week, I would have told you the late ice bite was "on," at least here in eastern Nebraska. I'm talking fish flying up off the bottom like rockets and absolutely smashing whatever I was putting down the hole, sometimes coming up 8-10 feet off the bottom in 17 feet of water!
These extended cold periods, though, have a way of messing with that pattern. Maybe that's what you're seeing right now.
Only one real way to know when the slow bite ends, and that's to be out there fishing it when it does!