If you store the two toys together, exposed and the silicone touching, you will generally and eventually run into issues. This seems hit and miss with some people.

Here is what I personally do, in 2 different boxes I have several silicone toys all stored together. However they are all in their own individual zip lock sealing bags. I also try to avoid having them squished tightly together as it can misshapen them.

Essentially what is happening when two silicone material toys are touching for a fairly long period is that they "melt". Whats happening is the molecules of the silicone materials are bonding and fusing (melting) together. It's never happened to me with high quality silicone toys with the way I store them. But I remember when I first got into sex toys, I have a jelly toy, and a rubber toy touching together for awhile, and they "melted".