It isn't like with the Enclave where you could fight them every so often driving them from their positions. That would be fun to do. Ambushing random encampments.
Huh, when I completed everything I could in Fallout 3, I'd just turn the difficulty to Very Hard, take Dogmeat with me, 2 Stimpaks, a combat knife and no armour. I'd then try and storm the town of Bethesda. That done, I'd move to where the unique respawning combat knife (Stabhappy?) was, while finally heading to the raiders wearing pieces of power armour and then trying to kill the Enclave at the bottom of the hill. It was fun while it lasted

Unfortunately, I can't think of many places to do that in New Vegas, apart from kill Bighorners :/