Tech Queries: What is the Shelf life of a writeable DVD?

What is the normal shelf life of a writeable DVD? I had some data stored on a DVD, which was placed in a cupboard, and I pulled it out of storage after just a year or so to find that the surface had corroded. There are patches missing in the DVD which you can see through, and of course it no longer works. How can I prevent this and/or extend the lifespan of a blank DVD?
— Sonu Chandra

There is no specific shelflife of a DVD–it would depend on the quality of the manufacturing process in the first place, how well it was stored and the conditions it was stored in. Specifically, heat and humidity can hasten damage. In a DVD, the top surface is the most sensitive since that is where the data is written. You should not use sharp objects on the disc surface, always store it in an individual case and keep it away from heat and humid areas. Periodically, you should check and clean any stored DVDs.

To clean a DVD, use a soft dry cloth and wipe from the inside to the outside in a radial motion. For added protection, you can store discs in a cardboard box in a dry, cool area with packets of silica gel inside. Silica gel will absorb excess moisture. All these things will extend the life of a DVD, but to make sure that your data remains safe, make multiple backups in hard drives and use online storage services like SkyDrive.

What is the difference between QVGA, WVGA, VGA (in terms of mobile phone screens)? Which one will be clearer?
— Koushik R

VGA (video graphics array) refers to a resolution of 640 x 480 pixels–QVGA or quarter VGA refers to a resolution of 320 x 240 pixels while WVGA or wide VGA is a resolution of 800 x 480 pixels. There are various other sizes too; for example SVGA or super VGA is a resolution of 800 x 600 pixels. Typically, high-end mobile phones and tablets have a higher screen resolution, but that alone does not contribute to the overall image quality or clarity of the screen. The type of screen and quality of components also contributes to this. For example, AMOLED screens generally have a higher quality image with darker blacks and richer colours. Even the standard LCD can have varying quality.

What the resolution does contribute to, is pixel density, i.e., the number of pixels in a square inch. Putting a larger number of pixels in a smaller screen increases the pixel density. A screen with a higher pixel density will appear sharper.