The AI Models Index keeps tabs on premium model releases from 15 labs since...

https://riversexpertchat.cloudhinter.com/posts/what-happened-to-gpt-5-vs-gpt-4.5-lead-over-time

The AI Models Index keeps tabs on premium model releases from 15 labs since 2023, verifying each with release dates and blind-vote checks. Updated every two weeks, it shows a steady pace—new versions drop every 4.5 days on average in 2026