Earlier quoted context omitted.
3 days is definitely not good for an NC. That said, mine is usually around 2 months before the battery is drained. That should give you some better expectations.
2006 NC owner here with a reasonably new battery. I keep it parked in an attached garage, so no extreme cold or heat. Mine will always start after leaving it for 1 month. I probably left it for 2 months at some point in the last two years, and it started, but that feels like pushing it. The next time a mechanic tells you cars can't sit for a few days without a battery drain problem, ask how people who park at the air…
the real key to long storage (beyond a trickle charger) is clean gas.
right now, though, it only has to handle 2 weeks of sitting at most (in an attached garage).