For our month-long September trip from Illinois to Glacier Nat'l Park & back, I plan to fill our freezer with meat/fish from our local butcher - 25 meals worth plus a bit extra if we decide to invite friends to dinner. There's no problem with the freezer in our Lance 1685 (20.9'long) keeping that much Plus I'll freeze a few lbs of deli meat for lunches.
I'll do rough menu plans for 30 b-fasts/lunches & dinner sides and buy everything that's not perishable to stock in the trailer. We have two big plastic containers under the bed labeled "the store" and keep daily use stuff either under the sink or in the drawer under the dinette. So coffee, sugar, coffee filters, cereal, any canned goods on the menu, etc. get stocked ahead of time.
The day before we leave, I'll add fresh produce for a week, fresh milk, bread, etc. Works great & saves spending valuable hiking time looking for a grocery store. When we do stop at a store, it's a quick trip for produce/milk etc. Also saves money because often there is no close inexpensive grocery.
ENJOY!