@jalan00 Try not to get wrapped up in the wording used to describe treatments. To be honest, your father will most likely be in some type of treatment for AML indefinitely. It does not go away on its own and the only potential cure for this form of leukemia is a bone marrow transplant.
However, depending on the type of mutation that is behind his leukemia, medications can help hold it in check, some into remission.

Your dad is fortunate to be able to take the lesser intensity treatments such as azacitidine. Comments from members who are on this medication, it seems fairly well tolerated, all things considered. And they can remain on this for years.

The term ‘as long as it works’, well, that’s a bit of a grey area. Again, mutations can be challenging. Some mutations allow cancer cells to circumnavigate the chemo by going dormant or basically hiding from the chemo, only to reemerge some time later when conditions feel favorable. Some mutations keep morphing, adapting to the chemo. When that happens “it’s no longer working” and time for another treatment option.
In my own case, I had 3 mutations which were very aggressive. Azacitidine or venectoclax were not options for me, so I had several rounds of high intensity chemo which is not survivable long term, and then a bone marrow transplant. A good friend of mine, whom I met while mentoring her through her AML journey at my local hospital, had different mutations. She was able to undergo intensive chemo for 5 months and is in remission…has been for 3 years without a transplant. But she was also much younger. As we age, our bodies can’t process the more aggressive chemicals which can cause collateral damage. That’s why meds such as Azacitidine are so valuable. They allow treatment for older patients where aggressive chemo would not be tolerated well. Years ago, these drugs were not available and for older patients AML wasn’t survivable. These drugs are a game changer.

Your father’s doctor will have used your dad’s test results to assess the best treatment for him. He is already responding to this treatment and may be able to remain on it for years before switching to another treatment.

I think you’ll benefit from reading some of the positive stories from other members such as @lindagi who started this discussion a few years ago: AML, age 78, taking Decetabine/ Venetoclax, no transplant https://connect.mayoclinic.org/discussion/aml-age-78-taking-decetabine-venetoclax-no-transplant/

Wishing your dad well through this first month. As his blood numbers drop, he may feel pretty fatigued until the cells regenerate in a couple weeks. His immune system isn’t as strong as it used to be so caution to avoid exposure for illnesses from viral, bacterial or fungal sources. Wearing a mask when he’s in a closed setting with people is really helpful, and no gardening. Is your dad nauseated or feeling tired?