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.
True enough, but it makes sense. To me at least.
Look what happened to the SS Minnow. They left for a three-hour tour, only took supplies for three housrs and ended up eating cocnuts for the rest of their lives.
If I'm the Supply Officer for the Enterprise, I am going to have crammed as much as possible into those cargo holds on day one, and am going to be topping-off whatever I can every time that ship got within range of a Starbase or supply depot. I am not going to be eating cocnuts exclusively at any point in that "five year" mission.