Long = several minutes of cummulative cranking (better not crank it for more than about 15sec at a time or you'll fry the starter).

Hmmmm. It starts when it gets warm. I wonder if your fuel cap vent is plugged, and when the fuel chills, it shrinks and it's REALLY hard to pull fuel against a vacuum. Leave the tank cap cracked open tonight and try it. Does it whoosh when you take the cap off cold?

Not responsible for advice not taken...