Does anyone else notice Claude's performance drops after a few weeks of a new model release?

I've been using Claude regularly for the past year, and I keep noticing a pattern. When a new model drops (like when Sonnet 3.5 or Opus was released), the performance is incredible - responses are sharp, creative, and really helpful.

But after 2-3 weeks, something seems to change. The same prompts that worked great start giving more generic responses. It feels less "intelligent" somehow, like it's being more cautious or something got nerfed behind the scenes.

I'm not talking about the model actually getting dumber - I know that's not how it works. But maybe:

• Are they adjusting the system prompts or safety filters after launch?
• Running the model at lower temperatures after initial release?
• Does initial honeymoon bias make me think it's better than it is?
• Are they doing A/B testing and I'm getting different versions?

Has anyone else experienced this? Or am I just experiencing confirmation bias and the "new toy" effect wearing off?

Would love to hear if others have noticed this pattern or if I'm just imagining things.