This thread got a tad longer than I anticipated. So, at the risk of repeating myself, this is how I make a Mother Mold, so I can make quick and easy back ups.
When I get a well performing RTV mold, I box the mold in, cavity up, and pour a well mixed, lump free POP mixture over it. When it sets, work the RTV mold out. Let the POP totally cure and seal it. I use D2T mixed with alcohol as a sealer. When that is cured, you can fill the POP mother mold with the RTV of your choice and when that cures, you'll have a clone of your original RTV mold.
I had a project where a fellow was making custom chocolates and needed appx 10000 pieces so I made two MM's and many subsequent RTV molds from them to speed up the process.
In the picture bellow, you'll see the orange Master and the white clones cast from the MM's (They're the POP squares@ the upper left)
The point is that once you have a good RTV mold, you can have as many clones of it as you desire, with a minimum of work.