Honestly, when you do a technique like that and include time intervals as such, it really doesn't help the prospect memory that you want to build up unless your doing those time intervals on your own without assistance from a timer or anything. On top of that, every "x" minutes is in my opinion, way too often to perform reality checks.
In order to really get the full potential out of any DILD technique you need to train your prospect memory so that it will come into your dreams on its own without the assistance of anything. I feel that it would be very unlikely that you would stop in a fast paced REM dream to find out how much time its been since your last reality check. In the end it all comes down to what you think will work for you, but imo I dont think this technique would prove effective.