Blow drying your hair frequently can lead to dry, damaged hair and can fade your hair color more quickly. Hair that is chemically treated is especially prone to hair dryer damage, since the health of the hair has already been compromised. While air drying may take longer, the benefits are definitely worth it if you can find the time. Air drying is easy as it requires no special tools or time. You can multitask while waiting for your hair to dry; I typically apply my makeup as my hair is drying, for example. If you are still somewhat pressed for time, consider air drying your hair for most of the time and then finishing it with a blow dryer. If you do continue to blow dry your hair, be sure to apply a thermal protective spray before using any heating tools and consider keeping the hair dryer on a cooler setting.
Air drying is also more environmentally friendly and can save you money on your electricity bill (especially if you use multiple tools such as a blow dryer, straightener, and/or curling iron). According to a poll (summarized here: http://www.dailymail.co.uk/femail/article-2250701/How-time-really-spend-doing-hair-ladies-Answer-Ten-days-year.html), women spent about 15 minutes blow drying their hair each day and another 15 minutes styling the hair. For blow drying alone, that is 5475 minutes per year, or about 91 hours (3.8 days). In addition to saving money on electricity, you might also save money by making fewer visits to the salon by improving the health of your hair (less blow drying = fewer split ends = fewer trims).
I used to blow dry and straighten my hair every day when I was in high school, and the health of my hair definitely suffered from it. In college, I decided that I enjoyed having the extra 15-30 minutes of sleep or study time and typically resorted to air drying my hair on my way to class. Now, I usually shower at night and let my hair dry overnight in a satin head cap. Sometimes I end up with really nice waves in my hair when I wake up by doing it that way!