A little more clear math would be appreciated... also a numeric result is expected.
Although not exactly what you are asking, if you check out the home page (of minergain.com) you will see a CDT (Coins per Day per Th/s) for Kano / Slush that is updated every 15 minutes for the past week, month, quarter and year. Some of these are hidden on mobile phones so use a desktop to see them all. Obviously this the past - which has no impact on future "randomness", but should give some idea what the long term results may be. The one big thing to notice is how rapidly Slush is decreasing.
Thank you for your very good reply. CDT is even better argument :-) I was calculating CDT ≈ 0,00016 for slush in January 2016... but well, looks like I was a few optimistic (and probably wrong!) :-)
What I don't understand is: "The one big thing to notice is how rapidly Slush is decreasing."
Do you mean from "profit for miners" perspective? and from where you notice that?
I think what he meant was the Coin per Day per TH/s has been decreasing as you get closer to present time: