Accordionna mentioned seniors playing 72 bass boxes. I'm 71, slightly built, and have played full size 120bass accordions. About 10 years ago, I swapped it out for a "ladies size" 120. I have a gorgeous Petosa 96bass with a lovely sound, but then tried a chromatic button accordion. I hit "the wall" but loved the size, so bought a used Beltuna 72b from Liberty Bellows. This is now my favorite to play, specifically for the size and weight. If you intend to make it through Palmer Hughes, you'll most likely want a 120 bass, specifically for the later books, so I've found my three accordions (?! ) are the perfect collection for a permanent hobbyist.
Many years ago I bought a 48b accordion from House of Musical Traditions in MD, but swapped it out as I seemed to need more keys in both hands.