I purchased a case of Dan Arms Trap loads probably about 35 yrs ago. This is 12 ga 1 1/8 oz 3 dram equivalent load manufactured in Denmark. This case has been stored in a garage the vast majority of its life in the Carolinas so its been subjected to fairly moderate climate conditions. Any reason I should be cautious about its use? Will be used in more modern shotguns from 50's and up.

If well stored you should be fine. I have shot shot shells which were much older than that. I have shot surplus rifle ammo that dated before WWII. Properly stored it last a very long time.

Thanks KY. I thought the same but as I get older I become more cautious. When much younger I had some .303 rounds that dated back around WW1 if I remember and who knows how they were stored over the years. All I can tell you is that I had numerous hang fires on the order of 5 -10 seconds and that was exciting enough for me. Later I carefully opened up one of the rounds and found it was loaded with cordite.

Quite some time ago Tom Armbrust checked pressure and speed on vintage (20s-30s?) shotgun ammo - paper cases and fiber wads. He found inconsistent speed (he felt related to primer rather than powder degradation) and some loads had an increased pressure, he felt related to hardening/stiffening of the case and wads.
If the shells have a plastic hull I would have no concerns.
I didn't really think of 1985 as "vintage", but the music WAS terrible Madonna had 2 of the top 5 hits that year

Never mind Dire Straits and Phil Collins...

The ammo will be fine. It's almost new.

I've been shooting for competition for some time flats of Fiocchi 1 oz. target loads that my Dad bought over 35 years ago. He bought a whole lot of flats back then and they still go bang everytime.

I'm in agreement with Brother SGJ. Back in the late 70's/early 80's (?) I purchased many boxes of Dan Arms fodder for dove shooting; it's all plastic hulled stuff, and I'm sure they'll shoot as well now as they did then. As FYI a few months ago I purchased two loose boxes of Peters and Remington paper cased shot shells from the '50's and decided they should be used in a vintage double; so I went dove shooting with my 1902/03 vintage Baltimore Arms C Grade project gun. The shells performed perfectly, the shooter not so well; but neither were we skunked either.

Add Bob Seger to that gruppen. Roll Me Away-best biker song of all time-IMO

10 plus years ago I attended a local gun show and one of the regular sellers of ammunition made me a deal after I inquired about a couple of boxes of paper shells.
He asked if I was only looking for full boxes? I said no not necessarily.
He mentioned he had large boxes of mixed vintage paper shells and he would takes 20 cents a piece. We agreed to meet the ext day at the show and he would bring them to the show.
Ended up buying about half of them. ( should have bought them all.)
Have shot thousands of these shells at Eurasian dove and pigeons and 98% of them have gone off maybe another 2 or 3 % have a noticeable recoil or report change.
I think that’s a pretty good average since many of these shells are 60 to 80 years old.
I do use care in. Making sure the barrels are clear and look at the empty’s close on ejection.

I have shot many paper shells from the 30s and 40s in my vintage guns at doves. Every now and then I have a blooper, not many, but never have seen signs of excessive pressure. I will continue to shoot them when I can buy them reasonably.

For some reason I seem to get more opportunities to buy 16s than any other gauge.

Thanks to all for sharing your experiences. These are all plastic hulls and sounds like I should not have anything to worry about. Targets probably won't either 😳