i am also a premium member from past one year. but i have not earned, what so far you have mentioned. my take on this if u upgrade ur membership you will just earn double. like in my basic account i use to get 1 dollar per month but now with premium membership i am earning around 2 dollar. so its not a huge difference. the only reason my earning is increase because of task and offeres.
now i would like to know how to make 100 dollar a month... which is not true and possible.