In cases of starvation, it can take a long time. Fish have very slow metabolisms, so it takes a long time for them to run out of resources. In getting otos, I've had success in asking the LFS to give me one of their workers--most stores with planted tanks add a few to the plant display tanks to keep algae down. One from there and 2 that are new to the store, and you usually can get all three in good shape. That's how I got the 6 I have now--one worker from them, and 5 new ones. They are happy enough to spawn, some 9 months later. It's worth asking, at least.
