Is the solar charging capacity of your device still efficient?

I open this post to understand if Garmin's Solar devices have a solar charging capacity limited in time, coincidentally equal to the duration 
of the warranty. My Instinct 2 solar was able to exploit the full solar charging capacity for about 25 months, after which the solar panels progressively
lost efficiency over about 4/5 months and now I am not able to charge more than 5/6% even under full sun. Obviously my watch has not suffered
any damage and the screen is still perfect. In the post I opened ( forums.garmin.com/.../instinct-2-solar-progressive-worsening-of-solar-intensity- and-solar-charging-capacity )
another user also had the same problem two years after purchase.... planned obsolescence? Once the warranty has expired, Garmin only offers paid repairs.
Has any other user had a similar experience with other Garmin solar devices? I'm also asking because I recently purchased an Edge 540 solar and
I would like to know if it is destined to stop charging with sunlight when the two-year warranty expires.