Sometimes the client will disconnect itself randomly, there's nothing you can do about it. I have a script that refreshes the lobby every 10 mins and sometimes it will work for hours while I'm at the PC and then suddenly party decides to spazz out.
The only way to really keep it alive is set the script to do it's job every ~15 seconds (see below, add in your SN), and have it running a different PC/while you're asleep. I'm not sure what you're doing with partytools, but that might not be working either.
Code:
Loop
{
WinWait, PartyPoker.com: Poker Lobby - Good luck XXXX ,
IfWinNotActive, PartyPoker.com: Poker Lobby - Good luck XXXX , , WinActivate, PartyPoker.com: Poker Lobby - Good luck XXXX ,
WinWaitActive, PartyPoker.com: Poker Lobby - Good luck XXXX ,
MouseClick, left, 54, 97
Sleep, 15000
}