Before the final signing of a contract with a supplier or contractor, review their status to make sure they are still capable of delivering as originally discussed.
They may have tendered or quoted a long time ago and things may have changed (such as their workload, delivery schedules, material costs etc).
Even if you are still within the validity of the quote, they may have now booked a lot more work and may struggle to meet your expected delivery schedule. Suppliers or contractors may have said they can meet the price, but often the delivery time will slip. So check if they are still capable.