I also know that the rate is surely not - and it never has to be so - comparable to the F-16-rate during it's peak-time.
I agree that rate isn't necessary to be reached, more so because it got to 300 per year at one point, and in 5 more years it was above 250. But then again, F16 was produced for 7 NATO customers, during Cold war, when all those customers combined had to upkeep their air forces with combined number of fighters got approached 11 thousand fighters. And there were some extra F16s sold for third party exports in 1980s like Isreael, Egypt etc.
Actually, when one thinks about it, 250ish average production rate for combined air forces using the plane that numbered something like 11500 planes isn't that far off from what china is doing today. Ratio of 46 for F16 versus ratio of 48 or so for J10.
Anyway - again my feeling - is that 40-45 J-10s per year is quite low if You compare how many J-7/-8s still need to be replaced, the Flanker rate is also - again IMO - quite low even if I indeed see Blitzo's point
Current buy rate for chinese air forces is so high that, if china wanted to use their older planes for some nominal life time of 30 years, china would need to get more pilots and form more regiments. That current buy rate points to a 2400 fighter strong air force/planaf. So it's really hard to see how on earth the rate is not high enough. Some J7s were put into service just 15 years ago. A few regiments worth of J8 as well. Those planes certainly don't need replacement for another decade or two.
I don't think the flanker production rate of last two years is representable. Blitzo explained why. But we know SAC can make 24 per year, from the period of 5-10 years ago. And in that time, alongside those flankers, SAC made J8FR as well. So 30 or so planes per year is something SAC can do no problem, if the order/money is there. China is currently close to 80 fighters a year, i'd say. If it went any higher it'd suggest a 3000 combat plane strong force sometime in the future.
Important to keep in mind is chinese history of sticking to a steady production plan. Unlike Russia or US, who have these ups and downs, where at one point they're hardly producing anything and 15 years later they're making 80-150 planes a year, china has for decades now been steady and any increases or decreases have been gradual. In my opinion that's definitely the more efficient way to go about it.