@Strela
@Tonikill1
Kagurazaka Yuuki said that "failed" summons last around five years before dying. If they have "a year or two left" as written in past chapters, then we can assume they have been here for three years already.
They look more or less like elementary schoolers, so with a good memory they'd remember what hot chocolate tastes like. Though other than Gale who is obviously older, that's not set in stone...
...is all just my opinion. Though I'd think that's acceptable ambiguity, personally.