Variance question for those who play a lot of MTT's

[Emperor]

I have finished in a few final tables online in my day, but I am pretty sure my ROI is negative thus far.

Although I play mainly ring games. I would like to start adding a nightly MTT to my schedule to see if it will break up the monotony and encourage me to play the 4-8 hrs the MTT is going. However I am curious about the variance involved.

Let say I play the nightly 15+1 at Party, it averages 2K entrants. Lets say skill wise I am better than 50% of the donks in the tourney, but 50% are better than me (for now).

How many MTT's before I can ballpark my ROI with any confidence? (for stats guys, lets say 66% confidence)

Will it be worth my time? or Do I need to be better than 90% of the players skill wise to make it worth my while? (lets say worth my while is a measly $10/hr average over 100?? tournaments)