There are too many variables to accurately say when they should be added. Different variables such as source water, grain bill, style, etc can affect when the minerals should be added.
Programs like Bru'n Water are superb for this kind of question.
Caveat: If your beer is winning awards, by all means, keep on keeping on.
Minerals are used for flavor profiles and also effect the pH of the beer. Say you want to brew a DIPA and desire 350ppm sulfate and 70ppm Cl, adding all minerals to the mash could drive your mash pH down too far, past the desired range.
If brewing a darker beer, say porter or stout, and you want some chloride (say around 70ppm) to accentuate the maltiness, and you add all to the mash, you could again drive down the pH too low due to the acid contribution from the malt and from the CaCl.
Using a program like Bru'n Water (I use and user friendly) or Brewer's Friend figures out what mineral contribution, calculates mash pH, and allows you to hit the overall profile you are trying to achieve.
And I would +1 on the skipping of the 5.2 stabilizer. It doesnt automatically set your mash to 5.2