Thanks, everyone. Interestingly, I try to remember not to let my guard down. Yesterday my INR, on my Coag-Sense, was 1.8. (At the lab, it would probably be 2.0 -- another reason that I use a meter that seems to report slightly below labs). I'm not especially concerned, but I upped my 7.5 mg daily dose by 2 mg ONE TIME, and I'll check later today or tomorrow.
As Pellicle said, it's nice to keep an eye on it -- I expect that the valve will keep ticking until something else kills me -- but I have to remind myself to test weekly, JUST IN CASE MY INR DROPS... (Newer valves may be less sensitive to INR below 2.0, but not mine).