Ten times is probably a good number for deciding if you like a thing. And a hundred times is surely a good number for mastering it (or for beginning its mastery).
Degas thought you should repeat things the way that a ballerina repeats her dance steps or a musician practices a musical figure. You gain skill and sureness with each repetition. But sometimes you also gain ideas. The differences between one repetition and another can sometimes lead to new ideas. Thus it’s a source of invention in art.

“Il faut refaire dix fois, cent fois le même sujet.” You must redo — ten times, one hundred times — the same subject.

Certainly one hundred times is excessive if you don’t love the thing. But ten times is a way of gaining skill. And ten times offers enough repetitions to get to know the subject in a preliminary way — to learn it. With ten repetitions you find out if you do love the motif — whether or not it’s the right motif for you.

And if after you’ve done the subject ten times, you wish to explore it further then you know that your love is deep.
You could do ten versions of this, and ten versions of that, and discover through the process what kinds of things matter to you. Somewhere in that process you will find that the subject holds deeper meaning (even if you don’t know what that meaning is). At that point you want to plunge in and really explore its every aspect. Exploration leads to invention.

I have certain subjects that I return to again and again. I did not begin them with the idea that they would become my particular venues. I went into the subject innocently. But I was heeding some call — even if I was unaware.
I am not sure how many subjects I have — some I’m keenly aware of — the koi, flowers, seashells, certain kinds of landscape. If I did one hundred of each — GOODNESS — that would be four hundred right there!
Degas is a strict task master! But this is all stuff that one loves. It would be wonderful to do one hundred repetitions of each subject!
Today I’m beginning the Big Tidy Campaign of 2017 and part of tidying is taking inventory. I begin this inventory with an inventory of my thoughts — and of my fishes!