We get ecency points for using ecency. It's ours, we can use it how ever we want. Here r two ways to best usecase with reasoning:

Use 150 points to use it to boost someone else post.

Promote your post for only 1 day. If it's very urgent/important then 2 days are enough.

Reasoning:

The first one is simple, like self vote argument and it will never be properly solved I guess. So why 150 points is because to divide the stake between more other users. It will also be the best way to engage.

Promoting for 1 day is best because curation rewards decrease after each window that is 1,3,5 so if you promote after 1 day there is a chance some people will skip it (usually curators). Also promoting for 7 days will result in people hating that post as they will accidentally click it again and again. In extreme case they can mute u or even DV that post.

I will give this post a revisit and add more unwritten rules if I remember some more.