I looked at two companies that advertise in Sky and Telescope magazine, Beral Coatings (847-676-0330, and Precision Applied Products, 714-738-4775, and they list two or three different types of coatings offered. 'Protected Aluminum' with 89 percent reflectivity, 'Semi-Enhanced' with 92 percent reflectivity, and Enhanced with 96 percent reflectivity. Precision Applied describes their 'Regular aluminum' 89 percent reflectivity coating as having a silicon monoxide overcoating for durability, and their 'Enhanced' as having 96 percent reflectivity with a quartz and titanium dioxide overcoating for greater durability.
Clearly, for frequent use you want a good quality overcoating. But more importantly, you want the highest reflectivity you can afford. Consider that a 30-inch mirror has a maximum surface area of 706 square inches, not including about 20 percent obstruction for the secondary mirror. This would put you near a maximum collecting area of 0.8 x 706 = 565 square inches which is equal to the area of a 26.8-inch mirror. Now, if you use a 89 percent coating, your light gathering ability has shrunk to 0.89 x 565 = 502 square inches or that of a 25.3 inch mirror. Of course, your resolving power still remains that of a 30-inch aperture, however, the difference in limiting magnitude between a 100 percent coating and an 89 percent coating is about 0.13 magnitudes so there is a slight loss here.