A rate hold is a written commitment from a lender to give you a specific rate on a mortgage that funds within a set window — typically 120 days. If rates rise during that period, your rate is protected. If rates fall, most lenders will honour the lower rate at closing.
Why 120 days matters
Because a rate hold is essentially a free option on interest rates. There is no downside to starting the shopping process four months early — only upside.
Your existing lender is legally required to send a renewal letter 21 days before term end. By then, rate-shopping windows have closed and you're negotiating from weakness.