I've always maintained squawk, but I also am landing usually inside the SFRA where you really don't want to be ever caught squawking 1200. I'm pretty sure ADSE-X can actually show data blocks so stick to your discrete code.
I don't change off a code until I either shut down or am told to squawk VFR. Like Ron, I am in and out of the SFRA enough to be wary of seeing 1200 on the transponder. If there's no reason to switch to 1200 you might as well just stay on the code so they can see who you are.