pfSense

I decided that on my LAN I mainly wanted DHCP to be handed out to the static mappings and I wanted the static mappings to have very long expiration times.
I created a pool for actual dynamic mapping in the same subnet. I used this technique basically so I could provide shorter lease times to leases that were not derived from a static entry.

1) LAN - a) checked Deny unknown clients - b) checked Denied clients will be ignored rather than rejected.
2) LAN pool - did not check either of the above.

When above 1 b) was checked - DHCP no longer handed out addresses within the pool - it basically disabled the pool altogether.

Expected:
I expected the LAN to not hand out or respond to any DHCP request that was not statically listed.
I also expected the LAN pool to be consulted and for the pool to hand out an address.

as a side note: the 'default lease time' of a pool is not 7200 secs, it is whatever it set in the main interface - I did not expect the pool would use values from the interface if left blank.