Fairings are generally a good thing imho. The higher the winds, the more I like fairings - except in high crosswinds.
Heading into a wind, the fairing does what it does if you ride faster - make you more aerodynamic by smoothly shunting air away from your forward-facing flat surfaces - like the chest area. I feel like I have comparatively less problem riding into a 25mph headwind with a fairing than I would without a fairing trying to ride that fast.
Heading downwind, a fairing acts like a spinnaker/sail, catching wind and making you go faster with less effort. Gimme a super strong tailwind any day. I'll ride forever in those conditions.
Crosswinds are a mixed bag. From a forward quarter, you gain some aerodynamic benefit, but not as much as in a pure headwind. The closer to a true-crosswind/90 degrees to your forward motion, the less the aerodynamic benefit. From a rear quarter, same idea - more benefit the closer to directly behind you; you get less the closer it is to being a true crosswind.
20-30mph crosswind gusts are a definite pain in the *** and potentially dangerous if you aren't prepared for them. 40-50mph gusts would make me think twice about riding if there was no way to ride semi-sheltered from them. Something to consider about riding in high winds is flying debris.
I personally wouldn't ride in circumstances where I'd be out in steady 30mph-plus conditions for more than an hour. But that's because it would end up being "work", not fun.
On my Gold Rush Replica, riding with and without a fairing means being in different worlds - with the fairing moderate winds can be riding nirvana; without one, even moderate headwinds make a ride much more of "a pain"/similar to riding a cruiser in a sitting-straight-up riding position.