I started using No-Spill fuel containers several years ago, because other containers available locally were so lousy. The design and operation was just as it should be. The first version I had was the non-CARB model. The spout was not removable, you filled it from a second cap on the opposite side of the handle. I operate at landscape business and my containers are often left out in the sun. After three or four months, the containers all developed splits that allowed fuel to seep out. The splits all occurred near the handles. I had four of them, and No-Spill replaced them all under warranty.
The second batch all did same, but the splits occurred in a different location this time. All split in the indentation on the sides. The plastic seemed to be a little thinner in that area. These lasted just a little longer than the first batch. Once again, the company replaced them under warranty. You could argue that they should not be left out in the sunlight, and that this would never happen if they were not. But, in over twenty years, I only remember one other fuel container doing this.
The third batch were replaced with the CARB version. This time the failure occurred at the cap/spout. One lasting only about ten days before it happened. Be very careful tightening it. Snug it and quit.
Now, despite all that, the company has been great dealing with replacements. I don't think I have ever dealt with a better company.
So, be careful tightening the caps, and try not to leave them in the sunlight.