No absolutely not . Getting nightmares thinking about it.
Short term reasons: What if I realize something looks awful or forgot something or need to change stuff for speech bubbles when my writer changes his mind about wording or or or...
Long term reasons: I've needed the base colors for characters that I thought were one-time appearances and weren't, so those will always be available to go grab. Sometimes I want to use lighting tricks or a certain overlay color from way back that I don't remember - easy, it's all saved and reasonably organized.
Even if I need to flatten groups of layers to do more effects on them, I always keep a folder with the original layers standing by and make sure it's clear what I did in case I need to modify or dig through it. Disk space feels like a small price to pay for reversibility/repeatability.