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I've been playing this game sporadically since it was launched in, and, after having finished almost all of the events of the "Tier one" competitions, I still having doubts on how the career (Grid World) mode is structured.

As far as I've seen, you have a limited amount of races you can do for each "season", being both events and the "Driver offers".
- With the events you get the points for the licenses, so you can unlock new "tiers" and new events.
- With the race events you get money and the chance of try cars you don't have. Also, short races which improves your position in the classification.

The thing I don't really get is the LeMans event on the end of each season, and why the game is divided in seasons.

As far as I've played, the game is about completing all the events while getting enough money to get the good cars. There is any kind of limit to the seasons I can play with the same team? Can I just drive in Race Events for the rest of the eternity?

Is something I'm missing in the career mode? Always skipping Lemans will mess with me any time in the future?
Skipping LeMans just means that you will not get as many rep points or cash for the season, therefore you will progress up the leaderboard a little more slowly. I've never tried staying with the Driver Offers after I had the chops to race in my own team, but I would guess you can "complete" a career without racing with your team. As for "completion," you can continue playing wherever you want after all the cars and skins unlock (completion). If you repeat an event you will find that often although the races are in the same venue, the particular track configurations have changed.