Universal iMessage History and multiple devices

[JonD25]

I think I know the answer to this, but I wanted to check before making the switch and losing my history. So, I have iMessages and texts getting delivered to both my iPhone and my Mac. I noticed recently though that Messages on my iPhone is taking up over 4GB of space. I have it set to keep messages forever. What I'd like to do is back up my entire history (iMessages and SMS) to my Mac (recommendations for apps that will do this?), then set my iPhone to only keep messages for a year to help clear up some space. If I do this, will messages and SMS currently on my Mac stay put? And continue to accrue forever? I'm ok not having messages older than a year on my iPhone, but I would like to have a way to look back further occasionally when I want to.