I had a 138" Draper M2500 screen. First with a FPTV with 7" CRTs, and later with a FPTV with 9" CRTs. If you set a cap on the brightness and contrast being set to the standard factory settings, then you don't have to be overly worried about CRT burn-in or premature CRT failure.
But I agree with Lee that you can only get so big with a CRT FPTV before you take some hit in picture quality.
With my FPTV with 7" CRTs you needed an absolute pitch black room to get a good looking picture, and as he mentioned, even though bright movies like A Bug's Life would always look good, movies with dark scenes would turn black, and you would have to strain to see any shadow detail.
The extra light output of my FPTV with 9" CRTs helped a lot with the extra brightness bringing more life to the picture with better color and detail.
But the additional light showed off the downside of the high gain screen with more pronounced hotspotting and color-shifting.
Also, as it was mentioned, NTSC video does not show up well on a really big screen.
Overall, I'd also recommend keeping the screen size under 96" wide because you can go with a lower 1.3-1.5 gain screen with less hotspotting and colorshifting problems. Try and take the time to find some place local that has a high gain screen that you can look at with a variety of video material to see if the shortcomings of a high gain screen are worth it in trade for the larger screen size.
The larger, high gain screen was actually worth it for me, but I'd say that more than half of the videophiles would be bothered by the hotspotting, although most casual visitors had no problems with it. but you really have to judge the picture quality with your own eyes.