Since you are not going to be harvesting any honey from a hive of packaged bees any time soon, it would be best to treat immediately, preventing any problems. If the hive starts looking like it might produce a surplus, remove any medication before putting on honey supers. As a rule you can expect a new hive from package bees starting out on foundation to do well if they draw all comb in two hive bodies and fill the upper with honey for winter stores. This is especially true with the great demand for packages and the late spring deliveries we're experiencing this year. Ted Wout, 3rd year, 10 hives Red Oak, TX