The AI Models Index keeps tabs on premium releases from 15 top labs since 2023,...

https://source-wiki.win/index.php/What_Happened_to_GPT-5_vs_GPT-4.5_Lead_Over_Time%3F

The AI Models Index keeps tabs on premium releases from 15 top labs since 2023, verifying launch dates and using blind-vote checks for accuracy. Updated every two weeks, it shows releases now come every 4.5 days on average, a 56% faster pace