First time using. How sensitive is FEP?

I've done a lot of research but i didn't find something taking about how critical the FEPs condition is. I've cleaned it well but i tried that tank clean option and i had to use the plastic scraper to clean it. There are a few visible lines and indentations along it now (no punctures). Is this really bad or is it natural wear and tear? Should i replace my FEP?