Hi, first sorry for the question, i'm sure a lot of people asked it before but i can't found it with a nice explanation.

Sometimes algos like Skein are very profitable for 5-10 minutes, it's worth mining that time?
Is it profitable because the price of the coin is going up or because of coin difficulty changing? If that's the case, until the coin get auto exchanged it will drop the value again probably and it will not be very profitable right?.

Thanks in advance!