these will work indeed, but can i suggest another option? Ive really been pushing the word on Diatomaceous Earth recently. Fine powder, completely harmless to humans, pets, plants, but absolutely devastating to soft bodied insects (mites, ants, aphids, etc). basically heres how i did it for my aphids, and it solved it in less than 24 hours:
watered my plants. next morning i look at soil and see the infestation. i wait a day (this allowed the top 1/8" or so to dry as to not clump and moisten the powder) and sprinkle a light coating all over the soil. you can drown the soil if you really want, wont do any damage, but its rather unnecessary and if you have fans like i do you probably want to keep any dust in the air to a minimum.
next morning, all aphids are gone completely and haven't showed back up since. i wouldn't expect it to work this well all the time, i got lucky. but getting lucky like that also shows how well this stuff can work, so keep it in mind.
to answer the original question though, agreed with above poster. watch for bugs all the time. i inspect my soil once a day, but with only 3 plants and a tendency to go into the room and watch them frequently (during lights on of course) i notice changes in soil and foliage just about as quick as they can happen.