When does the novelty seeking wear off?

I've noticed my puppy will always go for the "new" thing, even if the choice is between something he really likes like boiled chicken or liver and a new vegetable or treat that he has never seen before.

This becomes problematic when I'm trying to get him to leave things/food/garbage he finds out during walks. He resource guards these things (but only outside on walks) and growls/snaps when I try to take them away. If I try to trade up with chicken or liver or pretty much anything else, he just ignores it and keeps trying to go for the garbage.

Today I finally managed to get him to leave some garbage alone during a walk by offering him a cookie he had never eaten before. But it's not really practical for me to figure out and carry entirely new treats to trade up with him for every walk.