Apple stores all of your iMessages in a nifty MySQL database hidden away deep in your applications folder. Since I got an iPhone ~4 years ago, it was about ~300 messages back and forth per day. (yes, I may have a texting problem!). I actually wanted to prank my friends by wrapping the model in a Twilio API, telling people I got a new phone number, and waiting to see how long it would take them to realize they weren't actually texting me.