This command opens a tunnel using plink and automatically closes it after seconds specified in secs=$((<time in seconds>));

Auto close plink.exe tunnel after timer

plink.exe -ssh <tunnel params using -R, -L and -D>  user@host "echo; echo; export PS1=;secs=$((3600)); while [ $secs -gt 0 ]; do echo -ne \"This tunnel will auto-shutdown in: $secs                             \\r\"; sleep 1; : $((secs--)); done; echo -ne \"Tunnel closed!                                 \"; echo; echo;"