Hi- I (lvl 130 nightlord) was repeating the Magatia Reuel's Elixir of Life Quest and now I am not seeing the quest available anymore. My current HP is 9073 (started doing Rueles around 6000). Is there a limit to number of repeats or cap on HP?
Yes, it becomes limited once you're able to reach 9.5k HP by level 175 (taking into account HP you can gain from washing out MP and HP gained from leveling up). It seems you've reached that point, so the quest is now 1/day. Note: this cap takes into account Olaf and Ellinia HP quest, so there's no need to wait on doing those until you hit the cap, it'll work out the same either way