Generally, avoid discretionary LSA budget changes during the two-week stabilization period. Keeping the budget stable gives you a cleaner baseline for determining whether post-migration changes are caused by the migration itself.
If a budget change is necessary because of demand, spending limits, or business requirements, make the adjustment deliberately and record the exact date and amount. This lets you separate the budget change from migration effects when analyzing performance.
The goal isn't to freeze the account. It's to avoid changing multiple major variables simultaneously, so you can accurately identify what caused any change in lead volume, quality, or cost.