Thanks for the thread Ajmat. From my personal experience it is nearly impossible to protect a cars exterior which is not used on daily basis.
Modes of failure:-
1) Broken windshield from Falling objects eg. coconut, utensils (yes my car is parked below a flats kitchen) etc.
2) Scratches on the paint - Thanks to children, jealous persons, flying debris, misjudgement while parking by nearby parked cars/two wheelers, artists who use cars paint as their canvas!
3) Dents- due to kids cycling around and vehicles moving around my car.
4) Colour fade- Sun, Rain, dust , excessive cleaning by a clean cloth
used by the car washing guy.
5) Wall paint - Gift given by building contractor while painting.
6) Oily muck - If you park your car near a Caterers kitchen. It won't go away unless you use dish washer on your cars paint :(
7) Theft loss - Prying eyes usually look for whats inside the car through the non-tinted (thanks to government rule) car windows.
A good quality car cover is solution to few of the above failure modes. The other solution is the discipline and hard work required to cover/uncover the car cover, fold and stock it and clean the car cover on a routine basis.
Following are the problems associated with car covers-
1) Thin car covers are easy to use but they dont last long and fly away in windy conditions.
2) Thick car covers as mentioned by Ajmat are a pain to fold, lift its weight and clean them. But they provide adequate protection.
3) Any car cover which does not have a belly belt and a way to tie/hold (using inbuilt rubber bands) the front and the rear portion is no good in winds. Never keep a brick on the car roof as my friendly neighbour did it for me to keep the car cover from flying away.
4) Last but important thing is some car covers stick to the body and are not exactly waterproof too. They take a long time to dry and it causes a abrasive slurry (dust and water) to form between the cover and the car paint. As the car cover moves in wind the abrasive slurry does its compounding work on the car paint.
So as Ajmat pointed out having the right material of the car cover is extremely important. Even if the cover is costly in the begining it lasts longer and does its function well. A minor tear can be repaired at a bag repair shop and the cover will last years. Thus you can save your cars paint and lots of other hassles related to it.
Thanks Ajmat