A cooler mold tends to provide larger part dimensions, but this can often be offset by a reduction in cooling time. It is generally worth the effort to perform a quick DOE to verify.
Concern: During an on-site training session, we were discussing how a cooler mold typically provides the best potential for a lower cycle time. In this discourse, one of the participants was explaining that they typically use mold temperature to achieve specific part dimensions.
My Response: As a class, we used one of their dimensionally critical parts and performed a small DOE with 3 different cooling times at 3 different mold temperatures. Once complete, a part molded 4 seconds faster with a mold temperature set 20 degrees F lower had better dimensions than before. This goes to show that just because you made a good part, a better process is not impossible.