BB, Warrior HP Boost skill - ASAP or doesn't matter?

Making a new warrior in GMS Tespia, I noticed that my HP went up when I put my first SP into the HP Boost skill.

Does this mean it no longer matters, in the long run, when you max this skill?

I think it's correct, since already existing warriors would have to add this skill too and if it depends how early you add it then most warriors wouldn't have the HP boost.