I had this issue for a while, without really thinking about it. For a long time, most of my reality checks were basically at random, whenever my mind would wander to the topic of dreaming and reality checks would I think to do them.

I guess you could say there are two types of reality checks -- random, and reactive. I've mostly switched to reactive reality checks, which I do in response to various dream signs or events in everyday life. I still keep doing the random checks out of habit, but I think the best thing is to have those reactive reality checks.

With a bit of practice, you should be able to notice whatever things/events you've chosen to reality check with relative ease, snapping out of whatever you're doing to instead do an RC. I'd say this is the real advantage of reactive checks over random checks. As you pointed out, you're usually too busy in a dream to think of doing a reality check, but if you've trained yourself to react to certain stimuli, then your chances of doing a reality check are that much higher. And, if you chose the things to RC to wisely, then you're that much closer to regular DILDs.