That's a really hard question, LBH, one that I've asked myself as well. My WH left while in between affairs and online "activities" and I did not know when he abandoned us last year, what was truly happening. When his double-life was revealed, the complexity and length of the deception helped me decide what was starting to be too much. Now he is lying to our daughter because she isn't fully aware of it all and there is so much pain from hearing that it puts me over the emotional edge some days, so there's another part of the too much question.
For me, if it helps, it's been the lies, and the sneaking under my nose, (which I knew about but chose to wait to confront as we do), which continue after d-day and the affair of WH is still going. In my mind, lying and sneaking are part of disrespect and if we are not respected by our spouses or primary partners, what good is it for us, really?
And I'm finally getting to the realization that if our WS's are out seeking other people, their interest in us is not there but we are interested in them and their lives, but what good is it for us and our peace of mind and OUR needs? It's taken me a long, long while to realize that-that now my own needs are basically being ignored by him and they amplified with pregnancy.
When we were together, I put all my energy into my marriage and daughter. I was the proverbial housewife, lived for my famiy and them coming home. Another part that's too much is relative to that, because while I worked so damn hard on making nice times for us all, he worked on sneaking and lying in return.
When I have started to be able to accept the reality of the deception to me, it's helped me work on the question you posed, "how much is too much?"
My neighbor has been divorced three years from a cheating man and says "you know". In your heart one day, you sit down with a thud, whereever on earth you are, and you feel it in your gut, your bones, your heart. You simply know. Without a doubt.
The other day it hit me like an oncoming car that I don't think he's truly coming back, and maybe that's a little bit what she means. Where I had to sit was a huge snowbank, but I did and the cold helped my thinking kind of snap as to what he's really, truly been doing behind my back.
And I will wonder, possibly forever, if it's going to happen again.
Is the pain tolerable another time? The further on we go in time, for me, it's not.
Also, the blatancy of his putting the affair on Facebook and other websites while still married haunt me and leave me feeling mocked and publicly humiliated, so for me, this is too much.
Lastly, my WH is "confessing" to family members, but not ending the affair and not living here, so that's rather clear for me as well.