I haven't updated my showreel in over a year. I might never update it again.
The showreel format was designed for a world where you needed to compress your entire capability into a VHS tape or a QuickTime file and mail it to an agency. That world is gone.
Today, the work lives on the internet. Individual case studies do more heavy lifting than any montage ever could. A well-documented project page — with context, process, and final output — tells a client exactly what they need to know: can this person think, and can they execute?
A showreel answers neither of those questions. It answers "can this person cut to a beat?" which is a different and less useful skill.
What replaced the showreel? The portfolio site. The case study. The breakdown thread. The process post. All of these formats respect the viewer's intelligence more than a thirty-second hype cut set to electronic music.
If you're still spending two weeks a year agonizing over your reel edit, stop. Spend that time documenting your last three projects properly.