After buying a bike with only 3,890 miles on it, and finding that the right side cam lobe and rocker were badly worn - I don't believe it is ever good to start the bike and let it idle on the sidestand. Also - the oil pressure at idle is pretty feeble, so excess idling is not good for the bike.
Is your bike sitting outside, in a carport, in an unheated/uninsulated garage, in the garage attached to the house, in the basement? It makes a difference to the bike what kind of temperature/humidity swings the bike has to endure. The temperature/humidity swings help to pull moisture into the fuel system and corrode the metal parts.
My winter storage is a bit over the top. I change the engine oil and filter, then drain the E10 fuel out of the tank, put enough Avgas 100LL into the tank so I can go for a long enough ride to get the bike fully warmed up, shut off the petcock just far enough away from home that the carb is out of fuel when I hit my driveway. I then disconnect the fuel line and drain the fuel out of the tank, I drain the carb if it has a float bowl drain screw. About once a month I put a battery tender on the bike and let it charge until it shows the battery is fully charged.
IF you choose to store the bike with fuel in it - it would be best if you can find a place to buy fuel that does not have any ethanol in it (Check PureGas.org to find a place near you.
http://pure-gas.org) Add Sta-Bil to the amount listed on the bottle.....and ride the bike long enough to get the Sta-Bil into the carb - then when you are done riding drain the carb float bowl if you have a drain screw on your bike. Get a battery tender - and only start the bike if you can ride it......don't let it idle on the sidestand!