How often should you use this to maintain the Husqvarna 10 Inch x Superlok Glass+ Fine Diamond Blade ?

It will depend on how much you are cutting, the thickness of the glass being cut etc. This blade is not able to do long cuts or thick work. This blade is a fine grit and best for blown work or solid rod up to 1.5 inches. 

Here is a video about using the dressing stick and what to look for as the blade needs to be dressed. 

https://www.hisglassworks.com/support/sawblades/how-to-use-a-dressing-stick-on-your-diamond-blade.html