I think I'm five out of seven, however the two trips in which I didn't see them were not within lappet-faced range (Cape Town and Morocco).
I think I've only ever seen them outside a national park/protected area once though, in Ethiopia.
I'm two for two in recent years as well - saw a pair on the way from Ishasha to Bwindi in Uganda 2013, and then saw a total of nine in Tanzania in 2014 (Serengeti, Ndutu, Ngorongoro and Tarangire).
I wasn't birdwatching on my Zimbabwe trip in 1985, although I did see a lot of vultures in Hwange - no idea what they were unfortunately.