What happens if you collect all three stones?

[F4LK]

I only have Orin left and wondering if I kill her and take her stone will I be able to continue doing my side quests or will I be forced into confronting the brain?

[juicy j]

there's no urgency as far as i've seen.

[F4LK]

thanks

[Mr. Otter]

You can complete everything that you have left. There is no timer after the stones. I would still advise you to complete everything before the final stone though, as you may come across more gear that might be better than what you have to help you in the final fights.

[MarkedAsRed]

You're warned when you do reach the Point of No Return during "Confront the Elder Brain" quest - prior to that you can tie up all your loose ends.