I aim for new weight every week at the moment doing lower weights but as I go up more weights it will become harder then 2 weeks then longer to go up weights of course. But as I've gone up the weights my reps go down I do less with going up more weights with becoming harder to do and not to over train to much.
You wont see any change in muscles if your not going up in weights your body will stay at the same level if you havn't changed in 4 weeks nothing will change with that if you do more reps you see strength and stamina change yes if not over doing it. But untill you get up the weights your muscles wont grow anymore being same weights for 4 weeks. Also if you over do things your muscles wont grow either.
I lost 3 stones = 42lbs Im well happy!