I've never had trick-or-treaters while living in Richmond, but I've seen them. The part of town I live in, The Fan, is populated by families, singles and college kids, and somehow, those groups seem to live near each other. So, there are some blocks that have sort of a Halloween block party. All the families on one block will arrange some organized fun as well as keep tons of candy on hand - some of the decorating gets quite elaborate. Some kids from the suburbs have been known to drive in to the Fan to "attend" the parties in the blocks. And vice versa. Most of the college kids are either out at the bars on Halloween, or they're having some kegger at their apartment - meaning no kiddies. Thankfully, everyone and everything seems to go on side by side with no hassles.
In Fairfax and Arlington while I was growing up, we would get trick-or-treaters as late at 10:00pm sometimes! Just depended on the weather, and sometimes on the TV programming for that night. -And the day of the week. School night Halloweens were/are always early evenings.