I wouldn’t be offended or think twice about it unless you’re going somewhere else for hours and food will get funky. I can’t remember last time I didn’t clear my plate but the wife and daughter routinely get a box

Just a month ago wife and I were out for dinner on our anniversary at probably the most expensive nicer places in town 2 dinners and appetisers etc pushing close to $200 without tip and we only had one cocktail each and she took her leftovers.

If you want them and are going to a movie nextdoor, you can also pay them to leave it in their fridge. I have done that a few times like 3 in my life. The server was happy for the extra bucks and I didn't have to walk around with food for a few hours.

45 Years?

Advice: No leisure suit or disco shoes!
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My wife says your friend is good-to-go with asking for take-away boxes.