If you take them once a quarter/year, they are fine. But if you have load patterns where you want to pay for what you use and not over provision the DB signific

If you take them once a quarter/year, they are fine. But if you have load patterns where you want to pay for what you use and not over provision the DB significantly then you can't rely on maintenance windows. I think we will get there eventually with even RDBMS getting solutions like Aurora Serverless but right now most of them don't work well.