Unlike Fallout 3 when you beat the Main Quest.
Why can't you continue after? I swear I don't play the last part of the Main Quest anymore. It kind of ruins the point of the game if players know this and don't pursue that last part of the quest if it means your character is done and best not to save during the last part of the Main Quest because that would mean.....New Game unless you have a back up save.
It really annoys me to no end that they did this.
So now every time I talk to Mr. House he's going to be pressuring me into defending the Hoover Dam from the Legion. Yay. Thanks devs for putting this negative aspect in the game. I was really hacked off the first time I was stuck at Hoover Dam and couldn't move forward after. I didn't it take it literally when Yes Man or Mr. House had mentioned that there was no return.
So now all I do is just do the quests around that last part since this is my 7th character in all my time of playing New Vegas.
If I have a suggestion for the next game. I'd ask they didn't do this in future Fallout titles.
So, now I'll never touch that last part again. Maybe for fun if I'm bored. But I don't plan on saving during the event of it.