yeah im sure it will not last very long i was only testing these methods so that folks who wanted to make a cast of the original part could do so, maybe you can post some links to how molds are made for those using this method and have never done this before i dont want to give them a link that would confuse them. but i most of the time use smooth on when i do molds it does last a lot longer. and i have not tested my method as far as how many molds you can get out of them so this gives me an idea of a temp use.i can definetly say that that method will work, but your mold wil deteriorate much faster than using silicone made for moulding.
a normal mold would last you around 60 copies
this wil maybe make 5 before major tears and cracks will show up.
but hey, you can always make a new one.
also, try and make a hard shell around your silicone mould with resin and fiberglass, this will keep your mold in place when you make casts, so no warping or dents occur. there should be enough tutorials on the great internets.
(source: own experience and we own a shop that makes moulds on a daily basis )