No software engineering manager at a tech company should spend less than 30% of his or her time coding. Whether managing a team, a division, or all of engineering, when managers spend less than 30% of their time coding, they encounter a significant degradation in their ability to execute their responsibilities.
I can’t say if coding should take 10%, 30% or 50% of a manager’s time, but in order to stay relevant team leads should keep their skills sharp. It is a really tough thing, though, since there are so many things a manger is involved with. It is very easy to deprioritize coding, even more so when your team is talented.