Questions about print longevity

[Shutterbug2006]

I wonder if anyone has experience using HP's Colorfast Adhesive Vinyl on an HP Z3100? I was told I can only expect 3 months before fading (indoors) with this product, but the person who told me this had no direct experience with the product.

I am interested in increasing the print longevity. HP seems to highly recommend using a vinyl pressure-sensitive over laminate for best results, but I have no experience using this type of product so I used a spray instead.

I made a print 36"w x 20", and then applied several coats of Krylon Matte Finish spray (product #KR1311) to it. It did not seem to affect image viewing, and it didn't affect my ability to mount it on a glass door.

It was the first time I've applied any adhesive-backed vinyl to a surface and I did a pretty good job mounting it dry. Subsequently a little research seemed to indicate that I might have had an easier time of it if I had sprayed the glass surface with water first, to help in positioning the vinyl to begin with. I made a couple of mistakes when I applied the vinyl, but found that I was able to pull the vinyl off (with some struggle) and reposition it to eliminate most of the air bubbles. I was hesitant to rub the vinyl with anything other than my fingers (through a cloth) to push the bubbles aside - and found I did not mar the surface whatsoever doing this.

My questions are; will the Krylon Matte Finish spray work? and would it have been easier to apply the vinyl to the glass surface if I had sprayed the glass liberally with water first?

Any tips would be greatly appreciated. I'm sure loving my new 44" Z3100GP ps printer. Prints on satin and matte paper are astounding, and the adhesive-backed vinyl prints looked pretty decent too.

[Colorwave]

Shutterbug-
I've done exactly the same thing as you with the same materials on glass.  Unlike you, though, I've applied quite a lot of other vinyl, so the air bubble part under the vinyl was not as much of an issue.  Sign installers use slightly soapy water or a ready made product for the same purpose such as Rapid Tac.  I think there is a surfactant in it and something that makes it dry slightly faster than plain water.
You are correct, that the proper way to protect the vinyl is with a clear overlay layer, but I don't have a laminator either.  For the pieces that I printed myself on my Z3100, I also used many layers of Matte Finish.  I wasted some prints doing that, though, as I think I applied to many coats too fast.   I've used a lot of Krylon before, and the layers weren't applied too fast for the clear finish itself, but the combination of vinyl, ink, and Matte Finish was finicky.  When I had issues, it formed air bubbles that I assume were from the outgassing of the ink.  
Regarding longevity, I only had my prints on an exterior window for about three months.  When I went to pull them off, the ink and Krylon had dried out so much that it completely flaked off of the white vinyl when I pulled on it.  I was left with ink flakes on the ground and a crumpled wad of completely white vinyl scrap.
Best of luck,
Ron H.

[enduser]

A lot who comment are from the sign printing world and haven't caught up with the HP pigment inks now used in WF Z series. They may think you're using the old, and quite common, dye inks.

For some reason no one can fathom, HP calls both their dye and pigments "Vivera".  Hence much confusion if you're not part of the art/photo printing world.