Having had solar panels on my roof for nearly 15 years now I can tell you that the 25 year warranty is optimistic at best. Our panel maker, Sharp, cannot replace panels under warranty (180W) because they no longer make them and have no replacement stock. We discovered this when we tried to exercise the warranty on a panel that failed.
As with any warrantied product there are likely provisions for that in the warranty - you should either get cash value compensation from them or an equivalent modern panel.
Just because your first attempt resulted in a 'no' doesn't mean you are without recourse...
Oh they were happy to replace my 180W panel with a 165W panel, but at the time such systems (like mine) are built as 'strings' of panels in series. So putting a 165W panel in took all of the other panels down to 165W (which in my case effectively removed one panel equivalent). The higher wattage panel was too large for the roof mount. We ended up replacing the panel with a Chinese equivalent (which was 180W and the right panel size) and basically threatened to sue Sharp for the panel cost. (which they ended up paying).
You have to be careful to match the panels though - slightly different specs can cause problems for your setup. The same goes for batteries - mixing new and old will degrade your new batteries. (Lead acid batteries at least)
