Don't think about repotting in August. Instead poke six or more holes in the soil to loosen the soil. The aeration will improve the health of the roots and will aid in watering. In August watering can be a problem. If the soil is damp, don't water.
Some exceptions are willows and cypress.
It is best to overwater such plants. For most needled evergreens you should wait until the soil feels dry - then water thoroughly. Observe your trees and learn their individual watering requirements. Malathion will take care of aphids. A strong water spray gets rid of red spider mites.