Including takeout, about once a month on average. This eating out consists of doing each of the below about 2-3 times per year
-I meet a friend for lunch (around $12 or so),
-we get takeout pizza as a family ($25 ish),
-get takeout sushi for an at-home couple date(30% off if picked up before 5pm, so about $30)
-we go to a sit down restaurant as a family or couple for dinner ( $40-$50)
-lunch out as a family while traveling or seeing some sight ($20-$30)
Time seems to fly for me, so doing one of the above about once a month on average feels like we go out to eat often. However, it's not so often that we stop enjoying/appreciating it.
Edited to add: I don't have much harder numbers than this, but DH and I cover all eating out from our personal allowances of $75 ea per month. However, these personal allowances not only cover this eating out, but all clothing for the two of us (other than gifts), any haircuts or makeup we buy, electronics, movies, and pretty much everything else that could be categorized as personal or entertainment spending, and often build up in our checking accounts because we don't completely spend them.