install IPK on LG SMART WEBOS TV

I am trying to permanently install my ipk on LG smart webos tv, or to keep the developer mode still (knowing that it remains activated for 50 hours)

This is not possible. According to http://webostv.developer.lge.com/develop/app-test/

Developer Mode is disabled when:

The TV has been rebooted ten times while the TV is not connected to a network (webOS TV v1.x and v2.0).

Developer Mode has been enabled for 50 hours.

The Developer Mode login session is terminated.

If you sign in to multiple TVs with one account, only the session of the latest TV that you sign in to is maintained.

After Developer Mode is disabled, the apps that are installed while you were using on Developer Mode are uninstalled, and you will be taken to the log-in screen of the Developer Mode app.

However, you can keep extending the session time before expiry.