Nice article by Catherine Connor in How Product Management Must Change to Enable the Agile Enterprise. She writes:
When development teams adopt agile practices, product management is often caught off guard by the amount of work added to their already overflowing plate. Agile calls for new product management skills and traditional staffing models do not typically accommodate the new product owner role. Given that most product managers are already overworked, how can they manage these new activities to derive more value from software projects and products?
The product owner role is a full-time job. Catherine notes that the folks at Enthiosys have estimated the product management workload to rise by about 50% when software teams adopt agile. In fact most companies are assigning a full-time product owner to each project. Do you have responsibility for 3 or more products? No wonder you're so exhausted.
The solution for many has been to implement the product management triad: one product manager for strategy; one product owner for technology; one product marketing manager for go-to-market. Learn more about implementing the triad in my (free) ebook The Strategic Role of Product Management.