Wouldn't worry about it. If they've been there 9 yrs then there is enough of a population there to drown out the noise from your 2 packages.
Any "dilution", if bad, will be selected out of the wild population anyway. "Survivability" is best thought of at the population level, not the hive level.
Any "dilution", if bad, will be selected out of the wild population anyway. "Survivability" is best thought of at the population level, not the hive level.