I went to Argos (a UK retailer) a few months ago, when I went in and bought the Star Wars advent calendar, the woman serving me was giving me this "you're special, aren't you" kind of look, needless to say it was awkward.
Whenever I buy a set, even if I'm in the recommended age range for a particular set, I still get a weird look from the cashier.
I am a TFOL, and I know that AFOLs get it much worse, but AFOLs do have the advantage of other people assuming that they're buying it for their kid.
Before I just bought primarily Bionicle and Star Wars, but know that I'm interested in getting Nexo Knights sets, it's gonna get worse.
"When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up."
-C. S. Lewis-