What is the normal age of the new lenses of digital camera in hot weathering?

I had used a SLR film camera with different lenses for a long period (more than 20 years) and they are great till now cause they were made of a glass but now most/all of the new lenses are made of plastic that may get deffect by sun light especially in hot weathering where the temperture in summer is above 45C (110F).
I used some small compact sony cameras which took good images but after 3-5 years i coud not get such quality and i do not know if the reason is behind lens quality or some dust on the lens.
I cleaned the lens with cleaning kit but the images still the same or little worse.
I'm wondering about the normal age of the lenses of compact and other DSLR cameras such as Nikon, Canon and Pentax especially in hot climate.

I do not know of any Canon or Nikon DSLR lenses that are made of plastic so this should be a cause of worry. Some lens housing are made of plastic, but these are of high quality and should not deteriorate under normal condition.

As a precaution, don't leave the lens in direct sunlight (afternoon sun) for long periods and never in an enclosed glass area (like on a car dashboard) in the sun. I try not to touch the lens surface as much as possible. If you use a good quality glass filter (UV), you will not need to clean the glass of the lens (only that of the filter which you can easily replace).

Plastic is used in construction. Only the cheapest compacts use plastic optics.

I, and many others, use Nikon lenses in the most insane climates and the main dangers are moisture and dust, not heat. In that respect nothing has really changed.

Temperature should be okay for the DLSR lenses as soon as its not boiling but what damage the lense is the moisture.