are winter leggings worth buying?

the leggings I run in are thick enough so nobody sees my undies when I stretch or do yoga, but still summer ones, meaning not made of fleece. I like them because behind the knees they're made of mesh so my legs breathe more easily. After exercising for 2 hours outdoors my legs ain't cold. The winter ones from the same brand are made of fleece and don't have this behind-the-knees mesh window.

If you use fleece leggings, don't they get too hot?