The parent breeds of the Golden Mountain Doodle will give you insight into health considerations and life expectancy.
Because the Golden Mountain Doodle cross-breed has only been around since 2013, there is not yet a significant body of research into breed-specific diseases or health risks. However, the most common parents of the Golden Mountain Doodle offspring are the Goldendoodle and the Bernedoodle, both of which can be heath tested for known hereditary issues.
Potential Health Issues to watch out for
The Bernedoodle panel tests for congenital methemoglobinemia, degenerative myelopathy, Sandhoff disease, neonatal encephalopathy with seizures, osteochondrodysplasia, progressive retinal atropy, and Von Willbrand disease. Bernedoodles can also affected by hip and elbow dysplasia, ocular diseases, and some allergies.
The Goldendoodle panel is a bit more extensive and tests for congenital methemoglobinemia, degenerative myelopathy, Ichthyosis, neonatal encephalopathy with seizures, neuronal ceroid lipofuscinosis 5, osteochondrodysplasia, progressive retinal atrophy, and Von Willebrand disease. Like Bernedoodles, Goldendoodles are prone to hip and elbow dysplasia.
Ideally, your puppy’s Goldendoodle and Bernedoodle parents will be clear of any standard genetic diseases on their respective genetic panels, ensuring a certain level of health for your GMD. Parent OFA testing (for things like eyes, heart, cardiac, hips, and elbows) may allay concerns about dysplasia and other problems in puppies, although there are non-hereditary factors that may contribute to dysplasia, even if there is no genetic pre-disposition.
Since the GMD is a cross-breed and each breed has its own panel of diseases (many of which are not common to both), if one parent dog is clear of disease but is a carrier, they may be safely bred with a genetically clear partner and the offspring will remain unaffected. However, if both parents are carriers of a common disease, a percentage of offspring could be affected. A conscientious breeder will, of course, be aware of this and will ensure that no significant health issue would be passed on to the GMD generation.
If you have concerns about your Golden Mountain Doodle’s health or would like the peace of mind of knowing whether or not they may be affected by genetic issues, you can have your dog DNA test by a service like Pawprint Genetics or Embark (two of the more well-known and reputable options). Of course, there is also no substitute for quality veterinary care and preventative maintenance like feeding a high-quality food, providing supplements as needed, and making sure your dog gets plenty of exercise for overall good health.
Other Common Doodle Issues
Gastric upset and food sensitivities are often noted in many breeds of doodles, so Golden Mountain Doodles are likely not exempt. You may need to experiment with food options if your GMD has any evidence of gastro-intestinal sensitivity and has had a negative test for common parasites like giardia.
Bloat is also an occasional issue in poodles and Bernedoodles in particular, so it is something for a GMD owner to watch out for. Risk of bloat increases if susceptible dogs ingest food or water rapidly. A slow-feeder may be a good option for your GMD just to be on the safe side. Monitor your dog’s water intake, particularly on hot days or after play, to make sure they don’t drink too much, too fast. It is also recommended that they are allowed to rest after eating and exercised immediately after. 
Genetic testing is helpful, but not all health conditions are quantified by a breed-specific genetic panel. Some issues are simply notable in the breed and things to watch out for.
Estimated Life Expectancy
The Bernese mountain dog is known to have issues with both cancer and heart disease, which leads to a shortened life expectancy. This is just one reason why the Bernedoodle cross-breed has become so popular; instead of the 7-year life expectancy of a Bernese mountain dog, the Bernedoodle is expected to live 12-18 years. The life expectancy for a Goldendoodle is currently 10-15 years.
Although the Golden Mountain Doodle mix has only been in existence for 10 years, it is safe to say that its life expectancy can be estimated at 12-15 years, if the parent breeds are a reliable indicator and you do all you can to invest in your GMD’s health through the years.