Less than that would be an iffy stretch for a longer-term power outage etc, while much more might stray into being too intimidating at first.
The sense of accomplishment from assembling that initial 'two weeks worth' should be a good motivator to add a couple/few things with each normal grocery trip.
Yes, 2 weeks prep for an emergency, gathering at usual grocery shopping.
And filling the car gas tank when half empty.
But we know - - -
We can suggest, urge, slightly frighten, and still many prefer to think “it’s not going to happen. . .”
Often they’re right, however, well, once it happens to them, or a relative - - -