Using 'In-Place' families embeds many of the project parameters/materials/object styles normally not present in a family which does have impact on performance and file size.
More importantly, there is no way to convert an 'In-Place' Family to a 'Loadable' Family so It is a 1 use only affair.
We tend to restrict In Place families to unique bench tops and unique landscape bits that won't be reused. I would rather spend a little more time on a parametric (changeable) family that can be reused than a quick In Place mock up.