It definitely would have been faster to go back following the same route we took when we drove to Imatra, but as it was Midsummer we opted for a slower, more scenic route to follow.
One thing you need to know about the Midsummer nights in Finland is that there is light almost throughout the whole night.
Driving on the motorways in Finland is relatively safe, even during the dusk hours when the larger animals, such as moose, tend to move around. But when you go for the smaller roads, there are no fencing to keep them out, so be careful and mind the sides of the roads as well!
Luckily the biggest wild animals we saw during our drive were rabbits or hares.