"Yes, most of the rubber used
"Yes, most of the rubber used after the late 70's is fairly resistant - todays gas does cause significant gumming problems however.
Even with the stablizer, filters etc I try never to run gas more than a few DAYS old.
Most Mfg's recommend now that you only put enough in the tank for your immediate use and even stablized, seal everything up tight (including airtight fittings over gas vents/caps etc) when not in use to keep the cooties out...
My youngest motor is 17, my other 3 are 21/21 and 22 years old - original gas lines, fuel pump diaphrams etc and zero "degredation" due to the gas and have never had a clogged carb - total run time between them in excess of 5000 hours -but always run stablized and whatever is left over after the weekend etc goes right into my pick-up - it doesn't seem to mind the 50:1 - especially after it's diluted by whatever else is in the tank.
Every outing the gas is only a few hours old in the boat...
But I am also super vigalent about storing them properly - "winterize" them completely if I don't expect to use any particular one of them for 2 weeks or longer and bring them back in the spring with a decarb, new plugs, filters, gear oil etc and flush them anytime they are run in dirty/gritty water..."