You want to avoid leaving ethanol gasoline in your fuel tank and system for any extended time period. Phase separation and water absorbtion of the highly hydroscopic ethanol leads to a corrosive mess...
Unfortunately I have first hand experience with this.
Several years ago I bought a 7 year old Honda ST1300 with just 7500 miles on it. When I asked about the low mileage, the owner told me the previous owner had let it sit up for a "while". I test rode it and all was OK so I figured no harm had been done by it sitting unused. Even on the 600 mile ride home and the subsequent 2 or 3 weeks it ran like a champ.
After about 3 weeks from puchase, it started acting like the fuel pump was going bad (started missing badly on acceleration). The ST1300 has an upper and lower tank with the lower tank containing the fuel pump. When I opened up the lower tank, here is what I found. A classic case of Ethanol phase separation, verified by someone I know who is a mechanic. He told me it was rare to get a rusted tank in his shop until Ethanol began appearing in gas. After that, he said he saw several per week, with more showing up after things sat up all winter:
Here is a diagram showing the phase separation process (discussion of the process HERE
It was not an easy fix. Even with doing it myself, it cost about $750 for parts (new tank, fuel pump & associated bits). It was a long job because the lower tank removal was pretty involved and tedious:
Since going through this, I always leave the bike parked with an absolutely full tank to prevent moisture laden air from coming in contact with the gasoline surface. If it's going to be parked for any length of time I'll put in STABIL and start the bike up every few weeks to remove any water that has settled to the bottom of the tank where the fuel pump pickup is.
I always use ethanol-free premium gasoline. There's no money to save with regular ethanol gas, with which it'd run like crap anyway.
This is very hard to find in areas in and anywhere near metropolitan areas due to environmental regulation.