Session Handling & Security

[eluser]comex[/eluser]
Two questions here,

1) I'm using an XML-RPC client that connects to my web server quite frequently. This client connects from a trusted source over the local network. But everytime it connects its handed a new session.
I store sessions in the DB and this will get quite cumbersome as the number of XML-RPC calls increases.
Is there any way to make just this connection "session-less" or to make it stick with one session?

2) Just a general question regarding session security. As far as I can tell codeigniter stores the session id and the userdata MD5d in the user cookie. The way I have things set up now the userdata part contains user_id e.t.c.. Is there any way to increase security on this process or should I just be happy with the way things are handled now? =)

Thank you!