Developing custom GPT in one single conversation

I’m developing a custom GPT, and using 4o version to interact with for writing code.

Using an XPS i9 16gb machine.

Experiencing "Wait / Close this page’ from browser,
and also error alert from chatgpt when trying to Copy first section from the answer, while it is still answering.

My approach was to keep the whole dev process in a single conversation, to keep the context, some uploaded files, docs and so on. But after few days, my interaction with the promp in this specific conversation become very slow…

What best practices you may recommand? Pro + Cons.