I admit, I often times forget to apply sunscreen while riding. Consequently, I just had a biopsy done on a spot on my forearm that the doctor says is "99% sure" to be basal cell carcinoma (skin cancer.) I'll know for sure in two weeks, and they will probably take a chunk of skin out of me. Luckily, it won't mess up any of my tattoos!

I'm considering getting a pair of sun sleeves but wonder if they really are too hot for summer riding. I have a pair of arm warmers for the cooler months, but I can't imagine using them during the summer.
Questions:
1) has anyone had experience wearing them in hotter (90+ degrees) climates?
2) is one brand better than another regarding SPF factor and blocking UV rays?
3) is white the best color for cooling while still providing protection from the sun?
4) recommendations for a particular brand you've had experience with?