According to OpenAI's FAQ, existing GPTs remain usable until the retirement date, subject to their access and workspace permissions. After that they stop running. Migrate before then with the checklist.
Source: OpenAI's Custom GPT retirement and migration FAQ. OpenAI says dates may change, so check the FAQ for your plan.
Keep reading
Custom GPT to Plugin Migration ChecklistA step-by-step checklist to move a Custom GPT without losing behavior.What Commonly Breaks When You Migrate a Custom GPTActions, tone, sharing settings and file handling are the usual trouble spots.When are Custom GPTs being retired?OpenAI lists December 11, 2026 as the planned retirement date, subject to change.