Raise them while the plan is being developed, with the actual proposed dates and structure. This allows the immigration implications to be assessed before relying on the change.
Keep effective and proposed facts separate
Identify what is confirmed, what remains uncertain and whether duties or support will change. Do not wait for a renewal or travel appointment to disclose a material operational change that affects the existing plan. Bring three dates to the discussion: when the decision becomes irreversible, when the operational change actually takes effect, and when the applicant next needs a document or an admission.
The order of those three usually determines whether there is still a choice to make or only a consequence to manage. Where a change remains at proposal stage, say so explicitly, because advice on a proposal is a different thing from advice on a completed transaction and mislabelling it wastes both. Hypothetical example: a contract research organization plans to move its records unit to a shared service centre in another country the following quarter; raised while the plan is a draft, the question of which entity will then hold the qualifying relationship can still influence the corporate design.
Raised after signature, it is only a problem to be documented. Put the date of the discussion itself on the record, because a question raised early and answered late is a different fact from one never raised at all.