Personally I don't set goals for online sites because I find it more demotivating and also it 'wastes' my time. I would rather write an article than spend 2 hours trying to find a survey or do as many tasks to achieve a daily goal. Some days are good with a well paid survey or study, and other days there is nothing. I take what I can when I am in the mood to do it.
That's me though, and I try to write an article each day instead as that to me is more important while I edit and write chapters.