Simply so, what happens if you stay longer than 6 months in Canada?
If you stay longer than 6 months under the eTA program and your stay has not been extended by Citizenship and Immigration Canada (emergency situations only), you will lose your travel authorization and not be able to use the eTA for future trips.
Secondly, how long can I stay in Canada without a visa? Most visitors can stay for up to 6 months in Canada. If you're allowed to enter Canada, the border services officer may allow you to stay for less or more than 6 months. If so, they'll put the date you need to leave by in your passport.
Moreover, how long can a UK citizen stay in Canada on an eTA?
6 months
How long can you stay in Canada on a temporary resident visa?
six months