"Doesn't perform in the first couple of months"
Are you really ready to give him that much time if he's not performing? If he's serving up garbage I'd hope it'd take less than a 'couple of months' to bring Burton in - And vice versa for that matter - Not just recycle players for the younger one, but hold them accountable for their form, and drop them if needed - As @betcats has said, this is a business, and a cut throat one at that.
Exactly. On the same train of thought I am not just going to give Luai one of the most important spots in the team if Burton looks better after the preseason just because Luai has been waiting longer. Make it a fair contest for first crack at the starting spot, I think they will both end up in the 17 anyway.