/r/Android... Is a screen protector necessary?

I've had my Sprint Hero since January. The day I got it I bought an Invisible Shield by Zagg and it's done a great job at protecting my screen. I there were a few times when it probably saved my screen (At one point, the small cube attached to the HTC lanyard was embedded in the screen protector and the indent it created took about a week to work itself out).

Recently I tried to reapply my original 10 month-old protector and I messed it up. Using the lifetime warranty, I got it replaced. The replacement came, but it had ripples from being bent at the factory (presumably... Nothing bent in packaging). I got that one replaced for free and it came yesterday. I put it on my screen and I must have used a bit too much of the application liquid and I was seeing a lot of distorted colors and the screen was unusable. I removed it, everything dried out and I am able to use it now, but I can't reapply the same protector. I doubt I will receive a free replacement, and I'm unsure if I want to wait another week and spend another $4 for another replacement...

Do you think it's necessary to use a screen protector? I'm fairly careful, but I know there will be one time when I decide to jam a pen in my pocket or something for some stupid reason. I am eligible for upgrade in January (I think) and I want to upgrade, but that's not for certain. Thoughts?