I just thought I would share some advice on how we store our bikes up here in the Great White North, so here it goes! Up here in Canada the normal thing to do when we store our bikes for the winter time! We 1 Pump the tires up to the max tire pressure(center stand) no accessory stand needed!2 Change the oil so you have fresh oil in it for the 5 to 6 months of storage. 3 Make sure it's not in a real cold area and put a dust cover on it and tied down tight to keep the critters out of the air filter area! 4 Disconnect the battery and remove it from the bike and keep it inside hooked up to a battery tender! Or like a friend of mine does he keeps his bike in a warm basement with the battery not removed, and just attaches his battery tender directly and let's it go all storage season!
Any fuel stabilizer? I think the longest mine sat for any given time between rides was maybe three weeks so I chose to go without using any this winter (we had some nice days this year that were nice enough to take a ride).
Another good idea is to put a goldenrod under the dust cover on the floor, it's like a low watt heater, keeps condensation from forming when the temp. fluctuates and that saves your aluminum from corrosion and pitting.
If it's just 3 weeks I wouldn't worry about it, but if you plan to leave it longer than 3 weeks I would put some stablizer in just to be on the safe side! If bad gas gets ran through the fuel system it can gum things up!