Not true... they expire at midnight on your check out day.
I did a split stay this past August to save money as it was our 3rd trip in year . Not thinking, the first day with no dining plan after 5 days of dining plan, I tried using my remaining snacks.... no snacks were available. I had forgotten about not having the plan anymore. We are so used to have the plan that it was like automatic to use snack credits. By not thinking straight, I lost at least 8 snack credits because I forgot that I would loose everything when I changed reservation. I was simply not thinking.