So just to make sure I don't miss out on skill acquisition, when is the 'optimal' time to use friendship/heart/marriage seals, assuming I want to get as large a spread as possible?
The wiki states that if you re-class as a promoted unit, you get one new skill from the base class each level, and then up to the promoted class (if applicable), but what happens if you're 20/20?
This is how classes work in the game
Changing classes will have you retain your level no matter what with the exception of promoting a unit, which you can only do once and it is recommended that you do it once you hit level 20 for the best stats.
When you promote, you get skills at level 5 and level 15. During your promotion, you can change between classes and when you do, you can gain all the skills from the unprompted version, then learn the skills from the promoted class. You could reclass in your unprompted state, but it might make things a bit more difficult and you're wasting precious parallel seals that you can use for someone else.
For example if I were to promote the Nohr Prince, I could then reclass to a different class like a Paladin or Great Knight with my Parallel/Friend/Heart Seal whatever, and while you level up as a Great Knight, you will learn the skills for a Cavalier before learning Luna and the other skills as a Paladin/Great Knight.
The best time to reclass is when you are promoted to get the skills needed. You can only get a certain amount of skills, but later in the game you get an item that can raise your max level by 5 and you can continue to learn and reclass until you get all the skills you want. But you'll need to grind to make the most broken unit possible.
