It doesn’t save you from mosquitoes already breeding in the old bodies of water. That’s why you remove all bodies of water that you can’t treat (if you can remove them). And then you set up your own population sinks which are the only realistic breeding grounds near your house.
Obviously it mostly depends on local geography. If your neighbor has a big swamp and your house is 10m away, then adding a couple of buckets on your property probably won’t do much. Even though I’ve heard that even houses in swampy areas benefit from this strategy due to the fact that mosquitoes don’t travel very far.
around 1500m2, shaped as a long rectangle (not ideal because I can’t treat the neighbouring plots)