Due to work and cold weather I have not been riding the GS much and probably wont be until after spring.

I have a  2001 gs and its currently stored in the garage.


How often (i.e. once per month) should  I start the bike and how long should I keep it running  just to keep things in ok condition when I do ride it in the srpring.   Is it necessary that the bike be ridden or starting the bike indoors sufficient?  I can take it around the block a few times or do I need to ride at higher speeds. 

I do have a trickle charger.  I have read up on "winterizing" the bike but I dont think thats necesarry since Im not really storing the bike. 

You need to ride for at least 15 minutes at or above 5K RPM. Below 5K, you're not really charging the battery. Honestly, if you have it on a trickle charger, you should be fine. As for winterizing not being necessary.. I'd say pull your battery, put it on the trickle charger, and either drain your tank or add some stabil. All easy procedures that will take less than 5 minutes to make the bike ridable again. Much easier than letting your carbs gum up, and having to pull them out completely and clean them. Just my $.02

How often should I take it out for 15 min. , once per month? 

I'd say weekly.. just my $.02

15min/week  is a bit much.  If you have the time, then do it.
Otherwise I'd say every three months.

If you pull the battery out and drain the float bowls(turn petcock to off)the bike should be fine for a couple months.
without starting it up.

Fuel is the enemy. Draining your float bowls should suffice for long term storage in a garage. All other remaining fuel in the carbs should evaporate with very little gumming left behind.

Not running an engine can destroy other parts of the engine, but I wouldn't worry about it, if it will just be a few months.

Keep your gas tank full. This will stop internal surface oxidation (i.e. rust) inside the tank. Also, the fuel stabilizator is a must..

In the winter I usually go out and start my bikes weekly. Just let them run until the heads are good and warm. If one is hard to start, it gets the battery tender. I don't use any stabil or anything fancy with the carbs. Just run 'em till they're good and warm and sometimes I rev them up a little to freak out the people next door... lol

The more often the better.  I got a bad tank of fuel, and in addition to that I probably let my bike sit too long with fuel in it.  I had an engine gasket replaced as well (which is most likely the big expense), but the total bill was somewhere between $800-1000, I don't remember exactly.  That was at the dealership, but still.

I left mine off for about 12 days during snow season (nevada) and I had such a hard time getting it running after that. Took me good 10 minutes to get it going... and the battery was dying from so many tries too...