Do Slim Line PS2s stop reading game disks after a while?

May be...

My old fat ps2 stopped reading game disks. It was my brothers but he gave it to me when he got a ps3 for christmas last year. It stopped reading disks after a few months. I am getting a slim line for my birthday I just want to know how reliable is it vs the fat ps2?

I've had mine for 4 years and its still going fine :)