Possibly. It depends on the size of the codebase and how many other people are handling maintenance alongside him. In a small codebase, 90% is way too much.

Possibly. It depends on the size of the codebase and how many other people are handling maintenance alongside him. In a small codebase, 90% is way too much. In a larger (enterprise-scale) codebase, 90% could be normal if there are employees dedicated to maintenance issues.