Transport Security Vs Dialog Security

In an environment where there are many initaitors speaking to a central target with frowarders in between, from what i can understand this best policy is to disable encryption on the endpoints, since dialog encryption will be enforced this is all that is really required, is this correct.

If the endpoints used encryption the message would need to be encrypted and decrypted at each forwarder resulting in slower perfromance, where as dialog encryption would only encrypt at the sender and decrypt at the target, so is this the best way to go?

Secondly is it best practice to open a dialog initally and send messages over this dialog for years never ending the conversation? This way the services only have to authenticate eachother once, if there are no reboots etc that is of course.

I would think performance wise sending each message and ending the conversation each time is a much greater overhead ? So would it be best practice to keep dialogs open and keep sending messages ?

Initally when i was learning service broker i thought that one must send a message and end the dialog until the next message, but i think the other way is the best option ?

Is this correct ?

Thanx