I can honestly say, YMMV - Your Mileage May Vary...but I would also like to know "how fast" are these prints fading.
For a test I made a 4x8 billboard sign using Oracal 3651 NO LAMINATE and regular Mutoh eco-sol ink - which is basically identical to Roland eco-sol. I just took down the billboard almost 4 years later and the print lost about 30-35% of it's color. Still readable, faded yes, but still readable and the sign faced West the whole time. This is Ohio - not Cali, so I'm sure there is some difference, but still...
If your customer thinks a print should last more than a year outdoors then you need to laminate. In your case, I would assume that a small/medium sized Big Squeegee and a flat table would be all you need to easily laminate small prints for future jobs.