some conceptual questions about DVD discs

[kenny1999]

In fact, I guess most consumer types of DVD discs are already protected by at least one physical layer on both sides of the disc, the protective layer should not contain any digital information and not be processed by the DVD drive laser or other computer components, a few scratch by finger or pencil, should not affect the contents of the DVD in any way isn't it?

Quite some time ago, I forget exactly what I was doing , the DVD disc spin inside the drive for an unreasonably long time and keep generating loud noise, so it raised raised my concerns, I then forced to eject the disc and I could feel the whole disc was heated up . Is it the worst situation? What did I do wrong? I remember it has at least happened for a couple of times after a decade of using computer, what was the most likely cause for that?

Is it really necessary to use anything to clean the DVD drive?
I am not worried about the drive, it's cheap. I am worried if it could damage my DVD disc, they are original and rare. In fact, if I handle the DVD disc with care and common sense - hold by the edge, keep it in box, don't throw it or drop it, is DVD disc good enough to last for many many years without losing any contents??

[hello_hello]

The "DVD disc spinning inside the drive for an unreasonably long time and generating loud noise" issue might be due to the drive having trouble reading it. Was it a burned disc? (although it can sometimes happen with pressed discs).

It's not unusual for a disc to get warm inside a drive. I assume the laser must produce some heat, along with the motor spinning the disc. I'm no expert, but I know often after ripping a DVD the disc will be warm when it's removed.

I'm no expert on disc longevity either, but rather than worry about the lifespan of an individual disc, why not make a backup copy? Or even copy the contents onto your hard drive as some sort of backup (until the hard drive dies). You can backup the disc as a single ISO file (kind of like a zip file for discs).
If you make a backup copy of the disc you can put the original in storage and use the copy without needing to worry about damaging it so much.

[Ghitulescu]

In fact, I guess most consumer types of DVD discs are already protected by at least one physical layer on both sides of the disc, the protective layer should not contain any digital information and not be processed by the DVD drive laser or other computer components, a few scratch by finger or pencil, should not affect the contents of the DVD in any way isn't it?
In theory yes.
Quite some time ago, I forget exactly what I was doing , the DVD disc spin inside the drive for an unreasonably long time and keep generating loud noise, so it raised raised my concerns, I then forced to eject the disc and I could feel the whole disc was heated up . Is it the worst situation? What did I do wrong? I remember it has at least happened for a couple of times after a decade of using computer, what was the most likely cause for that?
Nope, the worst situation is that the DVD will break inside, like it was the case with the first CD-drives over 40x.
Is it really necessary to use anything to clean the DVD drive?
I am not worried about the drive, it's cheap. I am worried if it could damage my DVD disc, they are original and rare. In fact, if I handle the DVD disc with care and common sense - hold by the edge, keep it in box, don't throw it or drop it, is DVD disc good enough to last for many many years without losing any contents??
This is at least everything you can do.