there is allot to take into consideration here mate…
they could be both printed with the best ink in the world and laminated. but one facing south and one north. the one facing south will deteriorate more than the other…
obviously the goal here is to minimize the ink fading. today with ink prices being shot down in price all over the place, we tend to forget about uv stability and the like.
without going into a long winded post, all i can suggest is for the ink being used to be a reputable one. for the prints to be laminated by a reputable laminate.
lamination can simply be clear vinyl and it will perform very well… but proper lamination films tend to have higher UV protection properties. this is what will stop the ink fading if abrasion and chemical damage is not the issue.
to be honest… i never guarantee any prints life but i do, do as much as i can to extend its performance. if i have to give a guesstimate i say "laminated, you will get about 3 years plus"