I think it's tacky to guest strangers in. I remember quite a few years back when AA was offering DEQMs on ORD>LAX or ORD>SFO, and lots of people wanted to be guested into the lounge during their "layovers". I feel like if you can't afford a day pass or a monthly membership, then maybe you shouldn't be doing mileage runs, or resign yourself to relaxing in the terminal.