I cant get 14 now b/c I dont do them anymore (rarely) but almost 18 months after not doing anything but rack deads I did 500 for sets of 6. Two weeks after that I did 545 for 6. Two weeks after that--CHIROPRACTOR's office-----
500lbs for 5 is my baseline strength on it. I will most likely always be able to do close to that without doing them much or at all. This is all from someone who squatting 500lbs for reps was like tying tourniquets on my legs (wraps) and a boa constictor around my waist (belt).
The most I tried was 620 for a single but that was well before I could get 14 reps with that weight. My best was 605x5 and 645x3 both with no belt or straps-just chalk and baby powder.