I believe the symphony hall in Atlanta has 2 NY D's. By looking at them from the audience, one is less than 10 years old, while the other is more than 10 years old. For most of the concerto work, I tend to see the older one chosen more often, while the newer one seems to get more use as an orchestral ensemble instrument.
The other major performance venue in the metro (solo and chamber performances by top-tier international artists) have 2 Hamburg D's. I think one is about 10 years old, while the other is nearly new. They are voiced differently, which is why performers choose one or the other, not because of any obvious shortcoming.
The number of hours these pianos see use is certainly limited, particularly in venues where every hour is a "billable hour" by the support staff on duty.
On the other hand, pianos in conservatory/college/university settings in concert venues are treated with more variability:
- as many as 3 concerts per day
- daily dress rehearsals
- regular class meetings
- regular ensemble rehearsals
- moved carelessly by non-professional stage crew
- pianos/halls are sometimes kept locked, sometimes not (unauthorized use as practice piano)
- less maintenance (per performance) than professional concert hall pianos
- institutional temperature and humidity control ( = typically awful)
As you can see, it's not unusual for a concert piano in this sort of environment to see 4-5 hours of use per day (including very intensive use as a high-level solo recital or concerto piano), during the busiest parts of each semester.