When do you know it is time to divorce?

When do you know it is time to divorce?
Is it when you can’t stand to hear the sound of your spouse while he/she is eating?
Is it when you make plans that never include them?
Is it when the slightest idea of getting intimate bring you a nausea sensation?

Once I read somewhere that when you lose the admiration for the other person is when things start to change.

I don’t admire my husband, and it hurts to say that.
In general, we have a good relationship; he is a good dad and a great husband who does his share around the house.
He has a job and is the one who pays the majority of the bills.
He has no addiction, and despite being a bit overweight, he still attractive for some.

He is clean, well groomed, smart and interesting.

My life would be so much easier if, after 12 years + 3 kids, I still felt the same way I did when we first met.

But if I am not the same as 12 years ago, why should I expect to have the same taste, the same plans, and the same love?

I never feel guilty when I am with the other man, but I do feel guilty for being this wild, almost fearless spirit that I am.
I feel selfish when I stop to think about it, and this is the question I ask myself: When it is the right time to divorce?