The most infrequent visitors, tour operators say, are white South Africans, many of whom have never set foot in the black communities so close to their doorsteps.
Foreign reporters have long been barred from visiting Tibet except for infrequent, carefully-managed tours organized by officials, and Chinese reporters also face restrictions; diplomats have problems gaining access and even regular tourists, from time to time.
Their albums and tours are infrequent, now – once every five years or so.
The cost, and the effort involved, meant that tours were also infrequent — scheduled and anticipated years ahead.
For now, the only way to do it is to go to their under-constructed website or to catch an infrequent gig, such as this tour-opening show in Brighton.
Eliot Brenner, an N.R.C. spokesman, said in an e-mail that the agency had also made several changes to its guidelines after the Byron case, including provisions that require inspectors to "tour areas that become accessible on an infrequent basis to assess the material condition and status of safety systems, structures, and components".
Demand for the tours remains high because the expeditions are so infrequent; the last was in 2005.
Bowie's film acting became more infrequent from the late 1980s on, his time dominated by one ambitious world tour after another.
While he toured South Africa and Australia with some success, his appearances in Britain became more infrequent.
The Who, for example, intimated, first explicitly in 1982 and then nudge-nudgingly at infrequent intervals since, that they were making farewell appearances – but are currently on tour 31 years on.
