Simpler gas equipment like mowers and generators don't have enough compression to really care about anything but ancient gas, and if you run any vehicle that is multi-fuel capable it can detect and adjust compression based on a fuel's capabilities.
Ive been repairing and fixing junkers of cars, mowers, ATVs, generators, and more for 30 years and not once has bad gas stopped something from running. I only remove it if it was clearly having water raining into the tank. In every other case where I couldn't start something after sitting around for 5+ years, it was from the gas gumming up in the carb or the shitty diaphragm pump, which generally means there is little to no gas left to start with.
I wouldn't even suspect gas of ever being bad unless it was atleast a few years old. If the tank was open it could have evaporated, if the tank was closed it probably ain't great gas but I bet it would still run in anything but a high compression application.