1- in 3 days your have nothing to sweat. I like to start my ski at least every two weeks if not set up for extended storage.
2- batteries can be hit or miss. I would expect at least 2-3 seasons out of a decent quality battery. Yearly changes seem excessive. I do not leave my ski on a trickle charger but it's good practice to do so as long as the charger has a way to turn off at full charge; over charging a battery decreases longevity.
3- use a ratio rite or similar device to measure your oil so that you do not have to completely fill the tank and you can use the proper ratio whether you fill up 1, 2, 2.5...etc gallons.
http://www.amazon.com/Ratio-Rite-Measuring-Cup-does-come/dp/B000I1YLGK
I use a 40:1 ratio.