Crazy,
Advice is for you to stop watching. It will drive you crazy!
Does it really matter what the statistics are?
They could say that affairs last an average of 18 months - (just a number - not a real statistic) - your H's is beyond that - so what does that mean? Or they last 5 years? Again, what does that mean?
Unfortunately, like MLC, it lasts as long as it lasts. And, I'm just guessing, but in many situations the relationship is already over for months - before an actual split - as there may be an attempt to "make it work."
If you ask some of the "seasoned" LBS here - whose H's (and W's) have been involved in dead end relationships - long after there is any joy or fun - I would think they (the LBS) would say - stop watching or reading too much into their make ups and break ups. Eventually, most will end, as they are relationships created upon lies and deceit.....
Just let them be....leave them be. Focus on something else - like yourself - or you can and will drive yourself crazy.
Hugs,
Limitless