I'm not sure that playing time would make much difference for a Class A amp. If you did your final biasing after it being on 1.5-2 hr, it should be stable after that, if your ambient is the same. I do recall, though, Nelson mentioning to check bias a week or two after putting it into service.
Anyway, you might want to keep track of the bias when you sense higher temps on the heatsinks, before making changes. This will allow a better feel for the amp's behavior. Based on my experience with the F5m, if it is running hotter, even because ambient has risen, the bias has increased. I'm anticipating further changes as the weather warms, so I am following it closely.
Like you, I am also running with smaller heatsinks. Is your chassis the regular 2U Dissipante, or the 2U Mini Dissipante (a bit narrower chassis)? From some of your inside photos, I'm guessing it might be the latter. It sure looks good.