The plastic outdoor furniture mildews bad. I clean it with bleach and it looks good, but not for long. The mildew comes back and I am afraid the bleach is damaging the furniture with so much cleaning. Anything else that might help and last longer?

The bleach will take its toll on that furniture eventually. You can buy a mildewcide made for outdoor furniture. A bit more friendly than household bleach. More sunlight and better air circulation will help too.