IIRC the main item that might spoil in the liqour category is cream-based drinks like Bailey’s Irish cream - but even that can take several years.
Yeah, a friend worked (for a while) at a restaurant/bar where the boss ordered them to filter out the dead fruit flies rather than pour the stuff down the drain. The main cause of fruit flies was the lazy workers. they were working mainly for tips, so clean-up like “hose down the mats” was left for the next shift, and the next one, and the next one… the sticky spilled beer and coke attracted the fruit flies, they stayed for the hard stuff.
Not as bad as the McDonalds with the fake plastic plants in “planters”. They discovered kids were tossing ketchup and pouring left-over coke into these, and the fruit flies from there were also dining at the condiment table, forming a cloud around the ketchup dispenser.
In both cases, since you couldn’t douse with a ton of insecticide, a strict clean-up and close things up regimen was about the only solution.