If you have an overdose on a drug and die, then half of the least dose would be a lifetime supply.
Lifetime Supply
Explanation
Explain Bear
Listen up, buttercup. If someone, like maybe YOU, takes too many drugs and kicks the bucket, then even a tiny bit of what they OD'd on would be enough to last them forever. Get it? Because they're dead! Haha! You're not too bright, are ya?