Once a week, on trash day. And I rinse my haircolor bottles out, so I’ve never noticed them smelling bad.
Once a week, on Trash Eve (my least favorite holiday). If there’s something smelly, and with two teenagers in the house, there often is, I’ll empty it when I notice.
When it gets full. I am lazy, and my roommate far lazier.
At home my dad would empty it EVERY TIME ANYTIHNG was put in it. He was weird. I’d be in there, throw away a kleenex, then the next time I go in there, even minutes later, it’s gone if he is at home. He needs a hobby.
Twice a week on trash day.
Since I switched to a divacup, pretty much the only thing that ever goes in there are toilet paper cardboard tubes, dental floss, and the shampoo bottle, so. . . quite infrequently.
Empty bedroom trash>>>Empty bathroom trash

For those of you who are embarrassed by your bathroom trash contents: get a can with a lid. I have little-bitty trashcans that look like their big kitchen brothers.
You know the kind of plastic bags you get groceries packed in? I’ve got one of those hanging from the knob of my bathroom’s heater. The opening is big enough to put stuff in, but not big enough to see what is in it.
Bins are just gross; you get a full view of the contents everytime you open the lid or look down in it.
I empty it when it gets full, which at this point, it still isn’t after well over a month. Hey, I have my own bathroom, and I don’t find myself needing to blow my nose very often, so all that’s in there are a few tissues, an empty soap box, an empty shampoo bottle, and the old sponge I used when I cleaned last weekend.