Oh for sure, I agree 100%. But it's nice to make back ups to abuse. The original discs are extremely difficult to find and I consider myself quite lucky for having what games I have now. I want to preserve them for as long as possible. These games are only going to go up in value and I won't be able to afford the. Replacing the lens is still MUCH cheaper then having to replace a game.
For example my friend has a Turbo Duo as well, I would only lend him a copy but never the original just out of shear paranoia...like I'm going through now with my Castlevania SOTN...luckily there's plenty of those around.