Hello Johann,
I'll start off by saying I don't think we have distribution data over temperature and frequency for the AD8310. Having said, I think we can piece together a pretty good idea of how much change you can expect over each variable and estimate a total change.
I think the least variation you can expect is over frequency. Take a look at Figure16 in the datasheet. At 60 MHz over 10 MHz bandwidth there is hardly any slope change - there is fractions of a mV change from 55 to 65 MHz. So let's just go ahead and rule that out as a dominant contributor for the time being.
The next biggest contributor is the temperature. Take a look at Figures 3 and 6. The biggest slope change is at cold. Vout varies by about 1 dB at the low input powers which is 24 mV. This causes about 0.4 mV/dB decrease in slope at -40 degrees C. Visually, you can see the error at 85 degrees C is about have that of -40 degrees C. So this should translate to a 0.2 mV/dB increase in slope at 85 degrees C. So if you had a nominal slope of 24mV/dB, it will vary +0.2/-0.4 mV/dB.
The biggest contributor is part-to-part variation of the slope which can be seen in Figure 17. There’s a nominal slope of 23.66 mV/dB is varies from 22 mV/dB to 25 mV/dB. Figure 17’s population size is a bit limited (roughly 90 DUTs tested). With a bigger population size this distribution may widen a bit.
So you can see with a bigger population size, a few non-typical DUTs whose temperature variation is wider than +0.2/-0.4 mV/dB (this is not unexpected) and the variation over frequency, you can see why the slope is specified from 20 mv/dB to 26 mV/dB as the min and max. At 60 MHz, I would expect the min and max to be close to 22 mV/dB and 25 mV/dB, respectively. I would say at worst, you'll see 0.5 mV/dB more at either the extremes, due to temperature variation.
Hope this helps,
Joel