With few exceptions, I've kept a sling on my shotgun for both deer and turkey seasons. On my first trip out, schlepping my father's Model 12, I noticed how cumbersome it was to go tromping through the woods with both hands full. By the next year, I had my own shotgun, a Rem 1100, and it sported a sling.
The big thing for me is having both hands free while I'm walking.