One typical element is the presence of old enemies or unfinished business. Just because they are retiring doesn't mean their past won't catch up with them. Also, relationships play a big part. They might reconnect with old friends or make new ones in their retirement. In many such novels, the magic master also has to deal with the loss of their former status and power in the magic community.
A common element is the struggle to adapt to a non - magical life. For example, the magic master might find it hard to do simple tasks without using magic. Another element is often the discovery of new purpose. Maybe they start teaching magic to the young or using magic in a different, more peaceful way.
Often, there is a search for a place to call home during retirement. Some magic masters may choose a secluded forest or a small village. There are also elements of self - discovery. They may learn things about themselves that they didn't know during their active magic - using days. And of course, there are usually some sort of magical artifacts or knowledge that they pass on or protect during their retirement.