I live in Texas, so I cant avoid the sun and my car is exposed to the elements 24\7 as I dont have a garage either. Ive had these tweeter going on 2.5 or 3 years now. How they sound will depend on how you position them, if you want in your face with great output then face them on axis (how I currently run mine). If you want mellow and great sound quality then face them off axis. I cross at 2kH, yes you can cross them lower just depends on goals.
I dont want to clutter up this thread but any other questions just shoot me a pm and ill be glad to answer them.