IIS 6.0 .NET Remoting and HTTP Keep Alives

All,

I have 2 load balanced web servers that host a .net web application
and 2 application servers that host the remoted assemblies for
the .net web application.
All 4 servers have identical configurations, Dual code Xeon 2GHz and 2
GB RAM. Web servers are on DMZ and APP servers are on LAN. All four
servers are networked at 1GB Full Duplex.

I have ruthlessly adhered to the 9 rules of remoting from
http://www.thinktecture.com/resourcearchive/net-remoting-faq /remotingusecases.
My problem is related to the applications performance when I toggle
the HTTP Keep Alive setting.

HTTP Keep Alives OFF (What I want as per link above)
When I stress test the web application with Application Center Test
which is located on another server on the DMZ with 100 requests a
second over HTTPs. It dies after approximately 7000 - 8000 requests.
I.e. 0 requests per second.
If I stop the tests and start them again it runs at approximately 10 -
15 requests per second. I have to perform iisreset on both my load
balanced app servers to to get it to perfrom again. However the same
happens again and again at 7000 - 8000 requests, the performance drops
to 0 request per second.

When I enable Keep Alives I.e. HTTP Keep Alives ON (3 seconds) the
application performs perfectly i.e. 100 request per second...
continiously.

Can anybody enlighten me on why performance drops after 7000 - 8000
requests?