On mature reflection/consideration
Definition 1 of 1
Pro Tip 1/3Time Element
Indicates thinking over time, not a quick decision. 
On mature reflection, he realized college was the right choice.
Pro Tip 2/3Deep Thought
Used when the decision required deep and lengthy thought. 
She accepted the job offer on mature reflection.
Pro Tip 3/3Complex Issues
Often used for complex decisions, not simple everyday choices. 
On mature reflection, the board reversed their previous decision.