I don't handle my birds as pets, only enough so that they're not having heart attacks if I have to doctor one, so I've never had mallards that tamed down. if you handle them and hand feed, they can become tame... and some will stay year round.
you do run the risk with real mallards that they'll fly off to other areas, or try to migrate, if you don't contain them or clip a wing.
rouens, on the other hand, which have the same color pattern as mallards, but are the size of pekins, are a domestic breed and don't fly well, don't migrate, and might lay year round. I've had some that did, and some that didn't, but I don't think I've had any start laying after we got out of summer weather.
if you bought ducklings at the feed store, they're more likely to be rouens than mallards, but the size of the bird will tell you for sure... mallards are quite small, rouens are one of the larger domestic breeds.