Here's the thing... it won't "slowly" run dry. Its a dry sump, so it'll have enough oil for full lubrication until suddenly it doesn't. My guess is that you caught it early enough that the bearings stayed sufficiently wet and you were just hearing the valves sticking. It *might* be just fine to keep running it, but I would be at least a little concerned that something might be damaged. A heck of an expensive piece of equipment to leave to chance if you ask me. I would be very tempted to at LEAST remove the valve cover and inspect the cams. If everything is ok up there, then the bottom end is probably ok. Be VERY wary of any new vibrations or if that tapping sound comes back. You should probably also bleed the oil pump... make sure that the new oil actually circulates and that it doesn't just pool in the crankcase.
If you want to be very meticulous about it, it certainly wouldn't be a bad idea (might even be a good idea) to check the bottom end... make sure in particular that none of the conrod bearings dried up as a failure there would be catastrophic.