This is kind of fun to figure out lol
According to this place: http://www.mre-meals.net/wholesalers.php
A pallet of MRE's is 40" X 48" X 48", and that contains 48 cases with 12 meals per case. So for 30 years at 2 meals a day he'd need 21,900 meals, so 1,825 cases or about 38 pallets. Stack them 2 high I guess that's 19 pallets on the floor at 4' X 4' each, So in a 4 X 5 arrangement, that's 16 by 20 foot.
You'd need kind of a large hidden room to still leave room for a drug lab and whatever other stuff you'd need to live for 30 years, plus some living space to enjoy the LSD trips, but I guess it's doable