Can we maybe switch this to last valid frame? The issue I have here is that the frame counter is only well-defined in a binary sense (nonzero = bad), but because we don't know what the usual rate is the frames come in, we don't know what a value of 5 or 10 or 100 means. Its also not well suited to build thresholds on top of it.

Using the last valid frame puts a real unit to this, because we want to act based on timeouts. Since the commented out timestamp already exists, I would just remove this.