Ya you're right, I guess just telling people to dry their pots out is bad advice.
For me tho, pots that ALWAYS stay wet on the surface and grow algae as a result, are breeding-factories for fungus gnats. So I let the top few inches (of a 2 gal.) dry out every few days. (I also use BT and nematodes weekly tho)
The greenhouse I work at is a different story tho. Algae and gnats on almost everything because they water too much. Then they spray poison for gnats lol.
1 easy gnat inhibitor is: Cover the tops of your pots with something. Lids, or 2" of hydroton pellets.....