Yes, they will last for a couple years. The sweet alyssum might die back in a freeze or really hot part of the summer but often comes back when the weather cools in the fall or warms in the spring. My dianthus has been green year round and I live north of Dallas. It blooms on and off through the winter depending on our freezes. You are further south, so you will have better luck with your new plants. I have found that the white flowering sweet alyssum can take the freezing weather better than the lavender kind that tends to just die. I prefer the white kind, but last fall found some six packs that were a mixture of the white and lavender on sale, so bought some and planted it. Not sure if it is all coming back or not, but I can hope. In the past when I planted the white variety, it did really well through the winter.

I love dianthus or sweet williams but I got tired of dead heading them.

The sweet alyssum's never took from seed's I planted.

My sweet alyssum reseeds for me. (the white kind) it can get lanky so I give it a severe shearing 1 or 2 times to keep it a nice mound.

I have several Dianthus in many colors. We had a hard winter and they just bloomed & bloomed. I'm going to always plant this hardy survivor!

I planted my dianthus last year and they survived the winter and have been blooming for weeks! They are in a part of my yard that gets partial afternoon shade.