Some researchers (many of them at the National Ice Core Laboratory Science Management Office) preserve ice cores. One, at least, preserves snowballs, as indicated in this report by KCCI in Des Moines, Iowa:
Woman Keeps Pet Snowball For 33 Years
Hunk Of Ice Stays In Bread Bag
Prena Thomas… has a snowball that she made in 1977. Thomas said that over the decades, she has never had a power outage that would destroy the cold hunk she says is precious to her. “It’s just like a little pet,” she said.