How Long Can Tachycardia Be Monitored Before Needing A Cardioversion?

I am an Afib patient. I’ve had two ablations and will likely need a third. I take dofetilide (250, twice daily), metoprolol (100, 3 times daily) and eliquis (5, twice a day). I’m on vacation and would like to avoid a hospital stay if possible. I have been in tachycardia for two days...yesterday I went to the ER and they knocked it down to normal rate with cardizem. It came back within an hour of leaving the er. It’s been bouncing around 115-125 for a day now. How long can tachycardia be monitored before I need a conversion (cardio-inversion)? Any suggestions on how to get it back to normal? I’ve been doing deep breathing exercises.