Context vs. Fresh Start – What Works Better for Custom GPTs?

Guys, I need some advice from people with hands-on experience. Especially if you’ve worked a lot with different custom models — that would be super helpful.

I’m curious about this in the context of testing and overall response quality. What’s the better approach: starting a new chat every time, or keeping longer-running ones that benefit from richer context? I’ve heard the opinion that a big context window can actually lead to more hallucinations, even though using it feels way more convenient and practical to me. Has anyone run into this?