on me:*:JOIN <- not correct syntax see /help on join
Actually that works fine. (see Collective's explanation)
NoPlex:on me:*:JOIN:#help: .timer 60 CheckIdle
alias CheckIdle {
var %chan = #help
if ($me !isop %chan) && ($idle >= 540) { part %chan }
}
This code checks every 60 seconds your idle time ($idle) and, if its equal or higher than 540 secs, it parts you from %chan.
Hope it helps:)