Credits are per NIGHT of stay, so if you stay, say, 7 nights, each person will have 7 TS, 7 CS, 7 snack credits. The entire bank of room dining credits is available to you as soon as you check in to use in any order you wish, and expire at midnight of the day you check out.
If you use one of each type per day per person, including your check in day, you will have no credits left on your check out day.