Hi 10knotshot,
Thanks for the feedback and for letting us know what you ended up deciding … and congratulations on your new mattress 
As you know I think you made a great quality/value choice and I’m looking forward to your comments and feedback when you receive it and have had the chance to sleep on it for a bit.
While the 2 lb polyfoam in the 12 in 1 customizable is a good quality material (in its budget range especially) … it’s possible that the soft layer was “on the edge” of being too soft for you so that even “normal” foam softening over time was enough to take you outside the comfort/support range that is suitable for you (see post #2 here). Since it’s a component mattress you could replace the soft layer with either a firmer layer of good quality polyfoam or even a layer of latex and you would have a mattress that you could use as a spare or as a guest mattress.
The latex comfort layers in the BestMattressEver would be more durable than the polyfoam in your 12 in 1 customizable.
Phoenix