What are the recommended values for Connection Draining, Idle Timeout and Port Expiration Period on AWS ELB?

on ELB, what are the recommended values for the following:

Port 80 Stickiness Expiration Period:

Current: 120s

Recommended: ?

Port 443 Stickiness Expiration Period:

Current: 130s

Recommended: ?

Idle Timeout:

Current: 90s

Recommended: ?

Connection Draining:

Current: 120s

Recommended: ?

Not sure if I have correct settings. I have currently two web server instances. The issue is most of the users switch from one server to another server often times. This let the users leave their $_SESSION's from one server and can't carry out to the another server. And does the long execution of scripts on the web app could be one of the possible cause of this issue? And should I recode my scripts to have a session cookies so even the users switch to another server, so they can carry out the sessions they have from the other one?