The industry standard for most solar panels' lifespans is 25 to 30 years. Most reputable manufacturers offer production warranties for 25 years or more, that is for those mounted on domestic roofs, clearly on a camper, they are likely to have a slightly harder life, but nonetheless, 15 years should be a minimum.
Some panels from 1982 are still going strong: "In the Swiss canton of Ticino, one of the longest-serving photovoltaic plants in Europe is in operation. The plant with 288 modules on an area of almost 500 square metres has been generating electricity since 1982. It is still running today."
You are talking about thick, heavy glass fronted panels in rigid frames. I sell flexible thin plastic panels. They are a world apart in terms of construction, and industry provided warranties.
With glass 20v panels (which you are referring to, and nobody wants to mount on their van roof as it takes them over 2m height, plus adds 7kg a panel vs 1kg) you tend to get a 5 year warranty maximim (That's Victron rigid 20v panels - some of the best in the industry). Renology rigid panels have a 3-5 year warranties. Their larger thin (plastic) panels have 5 year workmanship warranties. More on Renology later. Most of the industry don't give more than 1 - 3 years on thin plastic panels. They are bendy, flexible, and they can't know what kind of life they will lead.
The 25-30 year warranty you refer to are P
erformance Warranties. These are not to be mistaken with
Workmanship Warranties - the actual warranty period where you have redress with the manufacturer or supplier. Performance warranties are where they tell you you'll get 80% of rated output at 25 years. These do not override or extend the actualy warranty, the workmanship warranty. What they are is a way of saying how your panel should perform during it's workmanship warranty period (the 3-5 years),
pro-rata (as a % of, over time). They are a way of manufacturers to try and show how good their products are with (hard to prove) performance over time statistics. They are a marketing tool, and NOT a real extended warranty. If you go back in year 6 and say your panel doesn't work, it is out of warranty and the panel manufacturer isn't going to give you another panel due to the 25 year performance guarantee. However, if you back within the Workmanship Warranty period and can prove that the panel has degraded in performance faster than they claim it would, then they have to help you.
Domestic (house) solar panels attract even longer warranties as a) they are larger and a higher voltage b) are mounted in a location that will never move - so the best environment possible for a long life c) are sold for a much higher price. It's not unusual for 10-15 year workmanship warranties on these, which when you are spending over £10,000 is not surprising really.
Back to slimline plastic panels, the panels I have made for my company are the best I've found so far after trying various differing factories and construction types. They are completely encased on one type of plastic, EFTE and are as robust as I've found to date. I've gone 3 years now without a single failure of these panels. For a while, I gave a 2 year warranty even though I was only getting 1 from the factory, due to my confidence in the product, plus what seems reasonable. Now I get a 3 year warranty from the same factory and I pass that on. I could not be happier with these panels.
I did look at renology a couple of years ago, purely due to the 5 year warranty on their thin panels. However their response to queries was glacial and unprofessional, and when I looked into reviews of the company I found the most common complaint, by far, was people getting no response when trying to claim on the warranty. This is vital for me. A long warranty means little if you can't utilise it, and if I went down the Renology route, I'd be the one picking up the cost, not Renology. It all felt wrong, and I'm keen to sell the best I can get to my customers - its in my interest to keep everyone happy, and my waranty support time to a minimum.
Someone asked how long should they last? I have 1000's of panels out there, many over 10 years old now and still going strong. Of course, things do go wrong some times, and if a panel fails not far oputside its warranty period I'm very acommodating and will replace panels at a near cost (to me) price to keep my customers happy. As that date moves further away, I increase the replacment price gradually, but it's always far far cheaper than retail.