He has devoted the best years of his life to preparing his impromptu speeches.
Churchill has spent the best years of his life preparing impromptu remarks.smith, f. e., 1st earl of birkenhead
Je vous ferai un impromptu à loisir.
Some of my Arcanum bunkmates taught me a card game called dogs-breath. I returned the favor by giving an impromptu lesson in psychology , probability , and manual dexterity. I won almost two whole talents before they stopped inviting me back to their games.