I have a Leer on my Nissan 4x4 that I bought new in 1993, has been a good cap. I've replaced the lift cylinders just once in 15 years, and the clearcoat started peeling about 1 or 2 years ago. Other than that, no other problems at all - fiberglas, hardware or sealing. I had an A.R.E. on my F250 for 3 years before it was destroyed in an accident last year, it wasn't a good cap at all. The latching mechanisms were junk, the window weatherstrippings shrunk terribly and wouldn't stay in, had to replace the lift cylinders way too early. The fiberglas was quite a bit thicker - a plus in one aspect, too heavy for my needs. It did have the carpet lining, my Leer doesn't. I prefer it without so it's easier to clean/dry. If you plan to camp/sleep in the back, the carpet would be a benefit but for anything else I can't see the usefulness of it. When I was pricing shells after my accident last year, the Leer was about 1/2 the price of the A.R.E. - I definitely wouldn't pay what they want for an A.R.E.
My only other experience with a cap was a Brahma that I had on my 1986 Nissan, it was made from ABS plastic. It was a fantastic cap, I had it 8 years and it still looked as new when I sold the truck with 248,000 miles on it. I'm pretty sure Brahma is out of business, at least that is what I was told in 1993 when searching for a cap for the new Nissan or I would have gotten one instead of the Leer.
In most cases you will have to remove the cap and replace the mounting tape every "X" years. I have found that going thicker with the tape and really getting the cap clamped tightly so it doesn't vibrate at all will extend the time between replacing. I use extra clamps so it's equalized along each bedrail. I haven't had the Leer off the Nissan in 10 years and it doesn't get a drop of rain in. The A.R.E. kept my F250 bed soaked in any rain at all.
