Keep long-series reading enjoyable instead of turning it into a completion task.
Signs of burnout
You forget recent plots, resent the next volume, skim familiar scenes or choose the series only because you have already invested time.
Use a rotation
Alternate one series book with another genre, nonfiction or a standalone novel.
Pause at natural boundaries
Major arc conclusions, time jumps and changes of author are useful reassessment points.
Completion is optional
A reading log is a tool, not a contract. Dropping a series can make room for something better suited to your current interests.
Practical takeaway: Describe the reading experience you want in two or three appeal factors, then verify the official first book and current order.