You can and should taste your 2015 Bordeaux once they arrive. The wines are usually quite tasty, albeit primary for a few years. After that, I'd leave them. I enjoyed several 2009 wines when I was in Bordeaux this year, but not the First Growths. I would not hesitate to pop a Pomerol or St. Emilion young, but I'd wait on the Medoc, especially the First Growths. But that's just me.