Hello,
I live in Eastern Pennsylvania, USA.   I have both Carniolans and Italians.
 Italians seem to be more prevalent among beekeepers in this area, but I
prefer Carniolans.  When I order new queens I always order them.  They seem
to work well here, however I still  have some Italian colonies that also
work just fine.  I don't requeen every colony, every year.  I think my bees
are becoming a mix of both races (if this is possible).  I have noticed dark
Carniolan queens heading up colonies that look like Italian bees.  I have
others where the bees are all very dark.  My point is that a colony should
be selected on its own merit.  If a colony is cross, or does not produce,
the queen will be replaced.  If it is working well, then it is the one that
I will use for queens and splits. I think you have to do what works in your
area and just bring enough new stock in to keep the genetics diverse.

 I did try Starlines once.  They were great and really produced, until the
second year.  Then they superseded and became very aggressive and had to be
requeened.  If you requeen every year then you should not have this problem.

A long time ago I remember hearing or reading that in areas where a number
of different races coexist there is really not that much cross breeding.
 Again, I don't know where I heard this but it apparently has something to
do with the elevation at which drones fly.  One race congregates higher than
another.  The queen would fly at the same elevation and would attract drones
of the same race.  Maybe someone on the list could confirm or disprove this.
 I just wish I could remember where this information came from.

Ron Bogansky
Kutztown (eastern) PA, USA