I'm wary of long tunnels, been through the Tunnel de Frejus once & never again. Poorly ventilated, bad enough on 4 wheels, would never do it on a bike.
I remember the F650 rider who kept riding in to a tunnel fire a few years ago to rescue people. Saved quite a few but never came out after the last attempt
I came through the Arlberg Pass tunnel on Saturday... similair length to the Frejus tunnel at 14km.
Not really a nice experience and just pleased when it ended. The thought of a fire or even just a breakdown midway is really quite daunting.
I remember the F650 rider who kept riding in to a tunnel fire a few years ago to rescue people. Saved quite a few but never came out after the last attempt