They'll Never Forego Potpourri
Anyone between Gen X and Gen Z will remember what potpourri is. Every Boomer has it in their home, whether in the living room, bathroom, or bedroom. They are dead flower petals scented with oils that give off a particular smell. They're... interesting decor, to say the least.
Jeggings Forever
Jeggings were made popular in the early 2000s. Boomers caught onto the trend quickly because finally, they didn't have to wear uncomfortable jeans or skirts. Jeggings are designed to look like denim, but aren't, and therefore are more socially acceptable. The Boomers will never give them up (and they shouldn't!)