You're assuming that there aren't any diminishing returns on sense awareness as it pertains to dream stability. Unfortunately, in my experience there's huge diminishing returns, and this method could probably only add a few minutes to a lucid.
What?

DEILD-chaining and staying in the dream are two completely different things. I agree with what you said about letting the dream destabilize and get ready to WILD back, it's a good method. It doesn't make the second chain more stable though, in my experience.

Besides, a few minutes sounds kind of good to me. Most of my lucids are under 5 minutes anyway. This technique has of course been posted several times already and is used by me and many other people.