What job do you level as, what do you have your NPC set to?
I have been leveling as BLM/RDM 32 (now 31, thank you Clearite), with her set as "Shield". Other jobs can Chain with their NPCs, but I don't think I can as BLM, not even with a dagger and Enthunder.....
Tried Jugner Forest & Merphead Mountains, TW to DC, Rolanberry Fields, TW to T++, and Kazam, darrrnit Gobbies.....
Red Mage 99, White Mage 50, Black Mage 75, SCH 99, Summoner 14, THF 25, BLU 25, NIN 50, WAR 18, DRK 50, DNC 49, PLD 50. Goldsmith 72 +2, Cooking 60 +2, Alchemy 41, Fishing 33, Rank 8, Windurst, Lakshmi (Garuda, I weep for you)
Red Mage 26 White Mage 11 Black Mage 12 Thief 16, Cooking 1, Rank 3, Windurst, Quez.
Every 24 Hours (Resets at 8:AM Pacific time) you can get a new Signal Pearl in case you "accidently" drop yours. This does not reset your NPC's level although it may reset her armour. The new pearl comes with its timer reset though....
This means two leveling sesions in most 20 hour periods.
Must try it before they change it.
Red Mage 99, White Mage 50, Black Mage 75, SCH 99, Summoner 14, THF 25, BLU 25, NIN 50, WAR 18, DRK 50, DNC 49, PLD 50. Goldsmith 72 +2, Cooking 60 +2, Alchemy 41, Fishing 33, Rank 8, Windurst, Lakshmi (Garuda, I weep for you)
Red Mage 26 White Mage 11 Black Mage 12 Thief 16, Cooking 1, Rank 3, Windurst, Quez.
Yeah, I can confirm that dropping your pearl and talking to your NPC buddy at the Rendezvous Point will earn you another ready-to-use Signal Pearl. Doesn't seem to reset level or equipment. I also rated down on Allakhazam the blowhard who reported this possibility to a GM.
I think that your NPC friend should be able to be called at least every 10 hours, and should stay at least 2 hours, unless they're killed or sent away manually. I also think that if you send them away with full health, you should be able to call them again instantly, a la Dragoons.