How long exactly do decals last?

Two years, yes. No problem if they are stored in room temperature. 

When they sit for several years in heat like a garage or something is when they go south. But never fear, if it's yellowing you get, the sun can bleach them back usually. Just just a decal restore solution so they don't fall apart with water 

Oh. Nice to hear!

i scan my decals when I get around to opening a kit. It's really handy for printing new ones.

Bill

It all depends upon the decals themselves. I've had Microscale & SuperScale decal sheets that are decades old and work superbly. On the other hand, I've have had kit decals from a new kit that shatter as soon as they get wet. But, as a general rule, keep the decals in a sealed airtight bag for as long as you can before use, and you'll get a far longer shelf life out of them.

I'll second stik.  If you open the box, slip the decals in a Ziploc bag, put a book on it to get the air out, and seal it.  Put back in the box and try to store inside out of temperature extremes.

If you run across decals that have turned yellow, put in a Ziploc, seal, and put in a window with sun.  Most of the time it will clear them up.

Right there with stick.  Luck of the draw. 

If in doubt, invest in a bottle of Microscale Liquid Decal Film. If possible, test using an unused decal from the sheet. If it breaks up when you put it in the water, apply the aforementioned Liquid Decal Film

They Should; Catch My other post where you posted in the other thread. .

I always test a decal sheet that is very old.  Most decal sheets have extraneous writing, like name and part number, that are decals too.  I cut one of those areas out and but it in water.  If it breaks apart I know I have to recoat the sheet with decal film.

I second all of that:

• It depends on the model brand and the company that made the decals (not always one and the same)
• It depends on how they were stored
• If you're not sure, test a decal from the sheet, if possible
• If you're not sure, use a sealer product as others have mentioned (on that point, I have read comments elsewhere that some have even used Future to coat an old decal sheet; I have not tried this, myself)
• If the sheet is yellowed, you can try putting it in the sun and let the sun "bleach" them back (this hasn't worked for me).
• and there are probably more things to consider, that we haven't thought of yet.

I buy a lot of classic kits, second hand.  Old Monogram kits, Revell kits, Aurora, Lindberg, etc.  I generally assume that I'll have to source decals from aftermarket vendors.  It's easy enough to find most of the markings you might need, in today's market.

And as you go along in the hobby, you'll probably accumulate a decal stash, just as you can accumulate a kit stash.  Alternate subjects from a sheet, where you used the other subject in your build.  Generic sheets, like a set of US WWII roundels in various scales, or sheets of meatballs for Japanese kit, sheets of letters and numbers in all fonts, colors, scales, etc.  I pack my extras in ziploc bags and stick them in a binder for easy storage.

I used to take them out of kits and store them in a safe place. Guess what- I lost a few here and there.

The bleach in the sun trick works surprisingly well, but it takes a couple of weeks, and DON"T hang them on the inside of a window that collects condensation.

Be aware that when you seal coat a sheet, which is a good if last resort; you;ve created one big decal. You'll need to cut them out very carefully around the edge of the image when you use them.

As I said, I always scan sheets before they get anywhere near water.. I can usually print ones that don't hold up.

And think about painting your markings. It's a really handy skill, and while things like lettering can't be painted without a stencil, a surprising number can. British roundrels, German crosses, certainly Japanese hinomarus or what ever those red circles are called.

And one more tip- decals are rarely opaque. The printed color should be mixed to read correctly over white. I try to mask the area where the decal will go, for the simpler and bigger graphics such as I noted above. Make a copy of the decal sheet on paper. Put blue tape or Tamiya tape over the graphics your want to use. Run it through again. Cut out image from tape, a little bit small.

Put the mask down over white primer, or spray white in the area. Then leave it there all through the rest of painting until its time to place the decal. Remove tape, apply decal, admire bright color.

Bill

I'm currently working on a vintage Star Trek Excelsior model.  The decals were made in 1994, and the hanging in the sun trick did not work at all.  However, I have discovered that most of the  yellowing is on the carrier paper, the decals when applied are much less yellow.  I only had to use a couple of them, and the slight yellow tint looks like part of the paint design, and it looks ok.  The rest of the decals were from the Round 2 decal set, a great addition to the model, by the way.  You can use that decal set with both the vintage model, and the recent reissue of the kit.