Not to me. If you're going on a five-year mission, you wouldn't just take what you think you'll need for five years. You plan for the unexpected and take as much as you can practically carry with you, and still meet all your other mission/logistical requirements.
Which removes all the evidence value of this "five years' worth of food aboard" anyway. If at any arbitrary point you are stocked for X more years, then X can't be used to infer your mission length.