Starting Time

I was thinks as i wondered the wasteland of 0.5 what would the world be like to survive in at different times after the Apocalypse.
For example their would be less zombies and more spread out packs the depending on amount of time that has elapsed. And closer and more zombies if it has been recent, allowing more story ideas.
It would also affect the amount of loot still in towns depending again on the amount of time that has elapsed and vise virsa.

Thoughts?