Are you talking about the third step of the Magnum Opus? It says there that you should still have full orgasms because forced abstinence is bad, even if you should wait a few hours after meditation. But if you're not doing that specific thing for the creation of the male elixir, there's really no reason why you should force yourself to retain semen. There is no reason and it will not empower you better.
I wouldn't do it for more than 1 week. And adjust slowly. Lets say if you have been ejaculating daily, don't just suddenly stop for a week.
More over, you should experiment with this. Maybe you'll notice a point where it doesn't get more powerful.
As long as you can, though benefits may get minimal as time goes on, if you're a few months in, not much will change in yiu hold for another month, but cooming will reset things almost completely.
Learn how to retain semen through multiple orgasm.
But if that's not your desire, whatever.
There is no time limit for semen retention, the time is set by the person themselves.
There are no negative or positive effects
The only good thing is learning to control a very big addiction and mediocre addiction