I don't put in fresh fuel on each trip. Sometimes I don't get fresh fuel for a month or two (I have large tanks).
This way I never have to worry. It's not just for long term stabilization, but helps with water, etc. As I said, it's sort of a religious choice.
Same reason some like to use ValveTect on every fill up, not just when closing up for the winter.
This is my choice:
http://www.starbrite.com/startron
One nice thing about StarTron, they do have a dosage formula, but say you can't really 'over treat' your fuel with it, so no worries if you put in a bit too much. Also they say it's compatible with other stabilizers, so no worries about using it in ValveTect or if someone used Stabil (which is only a stabilizer for long term use).
I use it in all my small engines, my motorcycles, snowmobiles, etc. I should probably use it in my low use cars too.
I'm starting to sound like an advertiser... but here is their video that tells you what it's supposed to do. If it does half of this, I'm happy to use it:
Since you asked "what does it do over the Summer", I thought that would answer it.