I don't have that much experience, but with what little I've done, my method is to deploy them on downwind as long as I'm not going to make a sharp turn on to base and final. If I have to make a short turn to final, or if I am in windy conditions, I won't deploy them.

Bear in mind that flaps on a short final might lead to a tip stall especially if you happen to be flying a warbird. Flaps on a model plane in windy conditions can make landings erattic. Besides, if the wind is strong enough, it will slow you down anyway.

I'm sure that there will be a variety of suggestions to be given here. This is just one thought.

Bob