Assuming my chain is showing that it's worn and getting close to needing replacement due to chain 'stretch'. I know you can flip single speed chainrings to extend their life when they become worn. Can I flip the chain around to extend it's useful life? I doubt it would double it due to some overlap in wear on rollers, but possibly extend it a bit by putting load on the opposite side of the pins.
I would say that this won't have any effect.
Flipping the chainring on a single speed makes sense as you use the other side of the teeth on the chainring which have not been used before. But with the chain it's a different story: The stretch is independent of directions so reversing its direction won't change anything. Also on the small "rolls" in the chain links on which the chain lies on the chainring I wouldn't expect any effect as they aren't fixed in the links but can rotate and therefore should wear out equally all around their circumference.
buy a new chain if the gauge indicates excessive stretch- just as you should. if you are a fanatic about extending your drivetrain's longevity- keep everything clean and lubed to the highest degree you find practical. and if you flip it over (there are FOUR different ways to fit a symmetrical chain)- remember- edges on the links will have to go thru the break-in process (link edges rounding off) regarding the left side of the larger chain ring (or chain rings if a triple) all over again- more so in a conventional crankset, as opposed to one featuring ramps and pins. i don't want to install my chain differently in any case- i mark it with a bread-bag tie before removal to assure proper orientation upon re-install. i ride my roadie only on the paved roads within my ranch- when i see dark sludge on my cog/chain ring teeth- its time for a cleaning/lube. after 4 years (>2K) of riding i have yet to detect any measurable stretch (love shimano chains). think about it- if you flip the chain over on the gauge- do you think it would measure differently?.....happy pedaling!