For non-mikrotik setup, I would stay below 35 to 40 pr RF-interface - that's what we see in real-life setups. The limitation here is in the 802.11 protocol - rather than throughput capacity.
However, there are a few tricks to reduce packet loss and retransmission on "loaded base stations".
Mikrotiks Nstreme implements the mechanism you would need to overcome these numbers - TDD, but it's MT proprietary.
For long point to point links, the Nstreme is priceless!