I get why someone people finally break down and have an affair, such as a sexless marriage situation or a spouse that is terminally ill or otherwise in a grave medical situation.
Having affairs to relieve boredom instead of genuinely attempting to revive the marriage instead is not included in that category.
If you're honest with yourself, you're not looking for a relationship, just someone to f*uck. If that is your thing then it is, but be honest about what it is.
Marriages are supposed to suffer ups and downs. It won't always be fun and exciting. Chances are she isn't feeling it either, so why not say so?
People in sexless marriage (as I am) struggle very hard not to cave. It's not about boredom or a thrill, it's about a loss of a spouse emotionally. There is a big difference between the two.