traditional green antifreeze/coolant 50/50 pre diluted shelf life?

There is no shelf life on unused coolant. It doesn't start to deteriorate until it's put into a car.

There aren't many cars that you can use that stuff on these days though.

There are some articles on the net which said that the silicates in the green pre diluted coolant are not stable because the mix with water and with time they begin separate from the coolant and the coolant become jelly and with particle residue,even if it unused.
Is it true?What is it with these silicates?

I don't know. I've never had an issue with coolant sitting on the shelf. Like i said, everything you should be using these days is silicate free. That green stuff is pretty much obsolete.