Forwarding Virtual Servers, SNAT Pools, and Port Collisions

I assume it's only the source IP and port that's being re-used; the destination IP and port don't ever change right. I wonder if your calculation is correct? The calculation of the 524s figure doesn't take into account how long the connections are open for. I assume the SNAT addresses are not used elsewhere? Also, can I assume no source NAT is occuring in relation to the client addresses before they hit the VIP?