VP U4.4 Question

No. I’ve left it in my tank all winter without issues

Another thing to consider, where will the bike be? This stuff can stink out your entire garage and/or house if it's not in the steel can.

Stink out or fill the area with a heavenly full race aroma?

I have left VP U4.4 in my bike twice for an extended period of time, about 5 months. Both times I left it in the tank I have had to replace the fuel pump and filter assembly. The other 3 winters, I drained it and my bike was fine. So, I say drain it! I could have just had bad luck, but at the same time the can also said to drain it. I have a 2015 CRF450 if that makes any difference. Even if I know it's going to sit for anything longer than 2 weeks, I transfer the fuel back into the can. A battery operated transfer pump is WAY cheaper than OEM fuel pumps. lol

I had it in my 19 crf250r. My bike stays in the house along with the vp can. Only time i smell the fuel inside it’s whenI bring the can back inside after fueling my bike from spilt fuel. Still own the bike with 81hrs no issues.

If the bike is mapped for U4.4 appropriately, it will run like pretty rich after the fuel has had some time to vent to atmosphere.

If it is only going to sit for a week or 2 between rides it's fine although you will lose some of the oxygenation in the fuel, it is recommended to keep the fuel in a sealed container when not in use.. If it is going to sit for weeks at a time or over the winter you should drain the tank and run the bike on good pump gas before storage. Some people will get away with letting it sit but for the 10mins it takes to drain the tank it's worth it. I recommend running a little 2stroke oil mixed with pump fuel before storage, race gas will corrode the piston/head and valves when left sitting for extended periods.

Depends on how old the fuel is that you are leaving in your bike. Fresh fuel straight out of a can should be ok to leave in your tank for a week or so. But if the fuel has been previously opened and has been sitting around exposed to air then you are taking a bigger risk. VP uses inhibitors to prevent the formation of gums when they manufacture the fuel. Once those inhibitors are used up then the rate at which the gums are formed accelerates quickly.
The vented tank will cause you to lose some of the lighter components of the fuel but generally not the oxygenates. This results in an increase in the oxygenate concentration in the fuel.
If you know in advance that you will be leaving the fuel in the tank for extended periods of time then add some fuel stabilizer when you open the a fresh can which should increase the amount of the inhibitors in the fuel providing you are longer storage time.