Couple years ago, I had five phones. Two iPhones, an Android, a Windows Phone, and a local branded QWERTY phone with analog TV. Back then, it started to feel overkill. Eventually I sold two of the iPhones and got my WP stolen.
But in the Philippines where Filipinos are gadget freaks/FB & selfie addicts, you pretty much need two phones or more and have two sims or more.
I only use three phones but I usually carry one (M7) when I'm out. We have dual sim phones to rectify carrying multiple phones. Sometimes it is better to have a cheap old Nokia as a backup. Alot of thieves and pick pockets esp in the bus or jeepneys. You have to be low profile sometimes. For me to own multiple phones is based on environment and thieves. We need backup phones.