My question involves personal property located in the State of: Texas

A friend of mine left a guitar, amp, cables, and FX pedal at my house, saying they would get more use with me, but I believe intending to get them back at some point. We had a falling out, despite which I attempted repeatedly to contact him and get him to come get them. There were dates and times set, none of which he made, or made contact for afterward. He has a couple of my dungeons and dragons books, which I honestly don't care about at this point, but thought would be worth mentioning.

He left this stuff here... 6 months ago? At the start of summer I suppose, and have been attempting to get him to come get his stuff throughout. How long do I wait before it becomes 'mine'? Or is there a set time? I don't believe he's ever going to come looking for them at this point, but I want to make sure I'm going to avoid any legal issues should I ever have to sell them.