To add to that, it is not uncommon to increase the max associations in high-density areas like you describe.
Reason that the default is in there, is that under normal (office) circumstances you should never go over 60 associations; and that limit will make clients pick another AP. That does not work for some very high density where you cannot place more AP's. Higher numbers of associations will give lower performance per associated client. If your design took that into account, you can increase that number of max-associations in your config.
In most cases you would not want that on all your AP's, and running the report like Colin suggests is a good start to see if your design and client estimates match reality. I would be very careful increasing the max-associations in your full environment as exceeding the 60 associations may indicate that you don't have enough AP capacity for office use.