It's actually very easy, as long as the community wants it. What you need is for someone to submit a hardfork proposal of the change, then the witnesses can vote on whether or not to accept the change. At least 17 of the 20 witnesses need to accept it in order for it to become active.
The question now is why? We have tried 24h + 30 days payout in the past, which was the changed to 7 days to make it easier and more understandable for everyone. I personally don't see a reason to change it, but feel free to let me know why you would like it differently.