There's no fixed time: some Operations last longer, while some—shorter than usual. When an Operation is over, a new one will start soon but not immediately: it might take up to few days before a new Operation appears. Don't forget that there might be other Operations running at the moment.
If you didn't manage to collect all the rewards that were unlocked by the end of the season, they will be automatically credited to your game profile.
NOTE: Any excess OXP will not carry over towards the following season.
If you didn't manage to collect all the rewards that were unlocked by the end of the season, they will be automatically credited to your game profile.
NOTE: Any excess OXP will not carry over towards the following season.