Man, I always get the hard questions!
Let me think long and hard on this one (no Bang Bros)...
Yes.
Whew. That took a lot out of me.
The likelihood, however, is another beast altogether. Then again this all depends on how old you are. If you are, say 16, then the chances that your boyfriend is banging out a 40 year old is pretty slim unless she's a school teacher, in which case, I'd check to see which classes he always has detention for. But, if you're say 20, and your boyfriend is too, then yeah he might be smashing off a 40-something year old. In college it was all the rage to knock off an older woman who could show you a thing or two. We called them sugarmamas.
You know, I completely overlooked another part of the question: you assume your boyfriend is cheating on you. Why wouldn't he just cheat on you with Heather or Becky. Why do you think its an older woman? Does he keep doing "housework" for this lady or something? Once again, this could be an age thing. Does he work for a firm where the partner is a cougar-esque woman who preys on young associates, because then yeah, he's probably totally banging her out - for his career!
Anyway, the answer to your question is yes. It is possible.
It was written.
This question is just...weird. There's no preamble or anything.
....?