How long can winter whites live?
1½ to 2 years on average, though some have reportedly lived longer.
Can winter whites be kept or interbred with other hamster species?
No, they cannot be kept with other dwarf breeds or Syrians. Doing so may result in fatal fights, so I rather you not risk it. I've heard cases of crossbreeding with Campbell dwarf hamsters (offsprings appear molted or are sometimes called puddings), but crossbreeding is not recommended because offsprings may turn out deformed (limbless or eyeless), stillborns, infertile, and have other genetic problems. Mothers may die while giving birth because babies are larger than normal. Also cross-breeding dilutes the 'pure' genes, so there are lesser lines that are either pure winter whites or pure Campbells. Once cross-bred, any further offspring produced by hybrids will never be pure.