How long do you all let gas sit in your carb?

Let it sit. Find ethanol free if you’re able. 

It is not a good idea to run the carb dry on a 2-stroke.  You are not only starving it of gas but also starving it of oil every time you do this.   You're fine with E-free.

I turn my gas off and lay it on its side to drain the carb while I move the stand to my truck. Running the engine till it runs out of gas is basically running it dry and that includes the premix oil that lubes the bearings. 

I drain the bowls on my vintage fleet…. 

This is my method as well. I also drain the tank and put the fuel (pump/VP110 mix) back in a metal can. Sometimes it might not be several weeks before I get to ride again and I just like to keep it fresh.

I never drain fuel anymore.

I feel PROPERLY treated fuel offers more benefits than not. By this I mean continuous submersion of fuel system parts to keep things wetted/lubed/protected against corrosion. This comment is in contrast to wet/dry/wet/dry cycles with draining that I've seen lead to undesirable deposits.

I continuously run Yamalube Fuel Med RX in all bikes, 2-strokes and 4-strokes, and strive to start the bikes every 3-4 weeks if they've been sitting (but in reality, they often go ~ 6+ months without being started TBH).

I also run Yamalube Ring Free Plus every other gas can refill.

This ^^^ has been working well for me for years and the bikes always start right up and the fuel "feels" fresh based on how the bikes run/respond. 

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P.S. I've also had GREAT luck with Marvel Mystery Oil fuel additive. The name turns many off, but it's got quite the pedigree and works amazingly well in a variety of ways - but my experience is limited to fuel.

Finding this out over time as well… every time I totally drain a tank dry, the petcock orings dry out & then leak when fuel is added back… I have been leaving some fuel in my tanks to prevent this.. I usually apply a little grease to the drain bowl oring when reinstalling…

I’ve never drained the gas in any two stroke I’ve ran with pump fuel. The premix seems to be an aid in not letting fuel varnish. Small carbureted four stroke motor? Run it til the bowls empty every time. 

Premix does a great job of tying up the "light ends" of gasoline. It works in very much the same way as fuel stabilizer. The exception is castor oils, as those can sometimes fall out of solution. 

I use Avgas in my vintage bike which is non-eth and let it sit for a year I think. I opened the carb and all that was left in the carb was pure oil. It wiped right out and the float bowl looked new, which it is. I was pleasantly surprised. I used to crack the float bowl drain because I was just going to wash the bike anyway and never let the bike sit for more than a month at the most a couple times a year.