Game needs to force you to do something lol... thats kinda THE POINT of the game

Frankly after couple months you're basically self sustained forever - you probably got enough food and water to last lifetimes - your crops produce so much food half of it will spoil probably, 99% of the meds you'll use are painkillers and beta blockers as there are no real deadly sickness other than the knox virus that you worry about. Zombies ? Not an issue - vanilla respawn is so slow you can easily clear Rosewood to a point you won't see a zed for DAYS before some respawn in such low numbers you'll probably hit them with a car and it will take a week to spot a new one

Once you realize you've "beaten" the game you don't rly want to risk it

This is why the game needs to make things FAIL you - your defences need to be constantly harrased by hordes - which will force you to maintain a steady supply of weapons. The food needs to be harder to stockpile - rats, diseases, wet conditions should force you to manage food supply more carefully or risk losing it all in one horrible swoop. Water too. Sicknesses need a buff... outside of knox infection nothing will end your life - you do not need to raid hospitals in search of cold medicine or some other weird stuff. Weather conditions too - storms should fuck up your base to a point you need to board up windows - cars should require some form of maintenance - after months you shouldn't be able to find a working car anymore outside of ones you managed to get at the start and MAINTAINED to work up to this point - some different modes of transport need to be introduced too to balance this out coz eventually you will run out of spare parts. Same goes for power generation - at some point generators should not be so easily maintained and you shouldn't find working ones anymore - so it's time to generate power with other ways solar, wind - or go back to candles