There's couple of reasons why PT invites really slows down after 50.
1. Most people is still trying to get Genki 1 done. Go to lower Jeuno, and you will hear people shout for help all day long for the item in Necro. (God I try to help as many of them as I could, but I can't do it by myself at my current level. I wish I could >.<)
2. Static PTs. Try to have a little log while you play, and find out what time zone people are from, and what times they play. So you can find potential static PT members. And you don't even have to have all 6. Try to keep it small, like 3 or 4, this will help you get a exp party going very quickly. Because life after 50, people are have so many things to do, such as AF, more Genki, a lot of farming.. etc..
One thing I've always remembered from a lvl70 friend.. He said, between lvl50-60, its SE's way of the weeding out process. The LFG time will be 10 folds on some days, and trying to get help getting coffers keys for weeks. (I've been there T_T)
All I can say is to just hang in there, you will make progress no matter what. I've find, fish, crafting, or farming an awsome way to kill time. But more importantly, its better to hang around towns such as jeuno, because I know first hand that most people who is forming a PT, will pick others in the same zone as them over others who are seeking at random zones.
Good luck to ya! /cheer
____________________________PLD 75 | BRD 75 | NIN 75 | BLM 75 | RDM 45 | SMN 60 | WAR 38 | WHM 37 | THF 30 | MNK 48 | SAM 10 | RNG 10 | BST 13 | DRK 10 | DRG 10
Rank: 10 San d'Oria | CoP: Complete | ZM: Complete
Fishing: 43 | Cooking: 52 | Gold: 52+1 | Bone: 10