Hello. That is a bit of a difficult question since so much depends on if his symptoms require treatment, how well Snookie is responding to the medication if it has been started & how well his follow up tests are. Dogs have been known to live only a few days after starting treatment, others have been on medication for 10 years or more. In general, we know the average life span for a Labrador is about 13 years, but to answer your question directly, the average length of time most dogs survive after being diagnosed with Cushing's is 24 - 36 months. I hope Snookie has many, many happy years, & please do not focus on the numbers. They are all just averages. Thanks for using Petco Pet Education Center, formerly Petcoach.