Hi and welcome to you and Jelly Bean
. MVD is always such a worry, though it's also hard to predict how or even if it will progress, though it generally does. Many people like to very much stay on top of the condition with scans and cardiologist visits. Others will work with their vet, and many vets are quite good at grading a murmur and knowing when to introduce medications. I like to have my affected dogs seen by a cardiologist for an assessment but I've actually rarely done ultrasounds unless there appears to be something unusual going on or more detail is needed to assess care. The approach for MVD is pretty standard and for many, maybe most dogs, I'd question whether lots of ongoing assessments and even interventions will provide any significant benefit to the dog.
At the same time, staying on top of progression in detail, could well add more valuable life time for a given dog, or prevent unneeded treatments, or help fine-tune care. It's really a highly personal choice and there'd be many views on this. One option is to continue to see a cardiologist but state that you don't wish to continue scans but would like them to do an auscultation, since their expertise means so much more detail will come from a simple auscultation than in one done by a vet.
There is no 'must' when it comes to care except to keep a dog as comfortable as possible. Personal means and care philosophies of course will influence what's done or not done by any given owner.
I think it's most important to have a good, capable vet whom you trust. I like my own vet because he is honest on approaches and I share his view that there are things that
could be done but don't necessarily need to be done, or could be done, would cost a lot, and might give a little more information, but wouldn't change the care approach or the eventual outcome. And then there are some treatments and imaging that carry their own risks or discomforts or quality of life impacts, with little real impact except to give more information.
Not everyone will agree with that assessment, but I think there are many ways to weigh ups what to do -- as long as a dog is kept comfortable and has good quality of life. Learning as much as you can about heart disease also will help you to weigh up the approach you feel comfortable with.
I hope all that might help a bit.