Your friend has an interesting hypothesis.  Where did he get his
information.  I started bee keeping last year and for several reasons, most
my own fault, received about 30 stings over the season, the last sting
produced severe hives and I was started on allergy shots.  The allergist
seems to have a lot of interesting ideas too.  His most recent statement
was:  "once desensitization takes place, it's best to continue getting the
occasional sting.  Articles he's read say that people who were beekeepers
and received many stings then stop keeping bees and don't get stung for
several years are at greater risk than if they'd never kept bees at all.  I
can't cite his sources but it's an interesting thought.
Karen