I've never waited more than an hour. I've also found that the seek flag doesn't matter. When I was trying to hit 70 to catch up to my static from lots of deaths, I tried out the old "seek party" flag once. In the 30 mins or so I left it on, I didn't get an invite. I turned it off because I didn't want people to think I was a mage that had to seek (they might suspect my gear was shoddy). I got an invite 15 mins later or so. I think a seek party flag is a turnoff to potential inviters. Also, waiting in Jeuno is a turnoff. I don't get random invites when I'm in Lower Jeuno. If I'm in a party in the middle of Ifrits Cauldron, I'll get <>Experience Points<><>Party<> <>Do you need it?<>. I'm never quite sure what to say. For one, anyone who's inviting me to a level 70ish exp party should know the darn color code in the /sea list. A classic conversation I'll never forget:
Inviter: <>Party<> <>Do you need it?<>
Me: I'm already in a party.
Inviter: I know, I mean an EXP party
I was in Boyhada with my static... I didn't even reply a second time.