Flat feet here too. For over 10 years I always wore sneakers with store-bought arch supports made by Spenco. Lower back pain prompted me to start wearing the orthotics. I even wore them around the house.

Around age 30 came the dreaded plantar fasciitis. I wore special boots at night but for years it nagged. Then I tried going barefoot as much as possible. I wore vibram five-finger shoes when I went out or crocs sandals. Mind you, I live in warm Florida and work from home a lot. Going mostly barefoot cured the PF.

It has been several years since going 90% barefoot/sandals and I've had no issues. I've found that for running it's more comfortable to have orthotics in my shoes. For cycling I just have the clipless shoe with nothing special. I think the firm sole of the cycling shoe is why I don't need the orthotics.

I think there is a different solution for each of us and perhaps a different solution as we age.