So I focused on the successor model (C620A) and decision of much better quality. No games at all.
So I am hopeful that the C620 takes a long time,
I must say that I spend ten hours a week telephone meeting, which would be impossible without the headphone jack.
His prédécessur had great autonomy (even eight hours almost non-stop without recharging it was still holding it),
to see if this model will keep its promises in this area.
Update after one year of use: still very satisfied. It holds well the load (more than 4 hours of talk time without recharging)
headphone jack shows no signs low: perfect!
