I've used them twice - once for indoor flying, once in the woods to protect against branches. If there is zero wind you can use them, otherwise don't bother and just be careful. Worst I've made contact with so far is a leaf which didn't really affect the drone (no guards), and this is my first drone so not like I'm super experienced flying or anything. I don't even know where the guards are now tbh.
Edit: read some replies, i just put it in the flymore case and fold the props in, no issues at all and I can't see a need for anything else.