I have a few people complaining about Idle Timeouts, I think it is something that has been set on the client rather than the server. I don't think that there are any timeouts set in pptpd or ppp does the following "CTRL" line suggest anything?
CTRL: Session timed out, ending call
CTRL: Client 63.12.xx.xxx control connection finished
Modem hangup
Connection terminated.
Connect time 26.1 minutes.
Sent 59320 bytes, received 18514 bytes.
Exit.