13 Pro Max here.
This is also my 3rd iPhone (I jumped on iPhone with Xs Max).
Very happy with this chunky beast, battery life is superb, iOS is incredibly smooth and fast on it, the camera is great and incredibly consistent, love how hefty it is and the display is pure perfection for all I do.
I am waiting to see the 15 Pro Max, if it is a good enough upgrade then I’ll probably pass the 13 PM on to a relative and jump on 15 Pro Max.
I have a 13 Pro too and it’s an excellent phone. I did buy it about 11 months after it was released as it was a good deal over the 14 Pro Max (£250 cheaper). I’ll probably get the 15 Pro Max but i’ll wait until the 16 Pro Max is released as that’s my strategy for buying iPhones now. I can’t justify these extortionate prices now, it’s got to the point where I feel it’s taking the mick. It may be that I end up keeping my 13 Pro Max even longer but i’ll assess it when it’s time to upgrade. I think my current phone will be good for a few years yet to be honest.