Every model since I turned 12
A lot of my decal sheets are based on aircraft that the decal maker had photos for, and I either couldn't find that same aircraft or when I did all I found was a profile somewhere. In each of those cases, I changed the small details that had to be changed to match a different BuNo that I did have a photo for. Of course, if I have a photo and the decal matches,,,,,,those get to be the "easy builds".
Many of my models weren't ever released as decals, but other aircraft from the squadron were, so those changes were made,,,,,for example to build an A-6C there is no decal for those,(because there is no model) but, you can get the squadron's A-6A and KA-6D decals all over the place, make a few changes and you can match your A-6C photo.
Other times, entire units were never released as decals, but, if you have a good photo and some decal sheets you can make something like a VA-26 Cougar or VSF-3 Skyhawk, or Blue tailed VA-43 F-11A Tiger.
Photos are also a must if you are doing something like kit-bashing to build your own -3 Fury, after you use your drawings to get things right, you need some photos to see if you have the "right look",,,,,,,you need that "3 D feeling" to see if you have what you intended.
Rex