Just seeking some clarification on these feats.
Ancestral Longevity - I original thought that it meant that each day you can pick a skill and become trained in that skill, so you could change the skill every day. Considering how Expert and Universal Longevity work, I now take it to mean that when you select the Ancestral Longevity feat you also select a single skill to which it applies. In effect it gives one extra trained skill with limitations (not counting as a prerequisite).
Expert Longevity - First paragraph, fine: when you select this feat you pick a skill in which you are trained. During your daily preparations you become expert in that one skill (and trained in you Ancestral Longevity skill). All good.
Second paragraph - so you can retrain a skill increase. Does that mean it can't be used on any skill that you had at 1st level? For example, if a character is trained in Arcana at 1st level then they can't become untrained in Arcana to become trained in their Ancestral Longevity skill by retraining. That seems odd, and also means you need to keep track of initial skills vs skill increases.
Also, and it doesn't say it, I assume that if you do retrain, then you need to select a new skill that will apply to the relevant feat, now that you are actually trained (or expert) in the skill that was attached to the feat.