I have a key to mum’s place, but I still knock if the main door’s locked, just in case she’s in the shower or something. If the main door is open, it’s because she’s expecting me - then I just shout through the screen door to let her know it’s me. I rarely do drop ins.
In the last few years, she has been the target of a stalker (long story) and might freak out a bit if somebody just appeared in her lounge room, so it’s better to announce myself than just walk in.
Nice follow-up question! My mom is a bad housekeeper, so if I wanted anything when I’m there, I’d ask first, but mainly t make sure the stuff is still edible. “Mom, is this still okay? Looks as if you may have kept it unrefrigerated.”
For non-perishables, if it will be missed (last cookie or apple) or if it looks like she might want to use it for dinner, I ask.
In the last few years, I mostly bring my own stuff and cook dinner for my mom and myself when I visit.
I just realized I usually do pop in with my dad. He lives in the same town as I do, but the main reason is that my dad, somewhat unusual, doesn’t really have or want privacy. He lives in a sort of artist-commune, where his liveing quarters and worlplace are all in the same room. People drop in and out all day.
Also, both me and my dad are hopelessly inadequate with our cellphones, and he doesn’t have a landline, so advance calls often fail on either the sending or the receiving end.
I don’t knock, and I do rummage through the fridge, but I’ll generally only take small things or parts of things (a bit of cheese, a few chips, part of a large container of cut-up fruit) without asking. I’ll ask before eating something substantial, such as raiding the leftovers, in case she was saving it specifically for lunch or dinner.
Things that she was specifically saving for something, like cookies for an oneg, will be marked with masking tape labels saying “DO NOT EAT.” Obviously, I don’t eat those.