An extension of the due diligence occurs when your agent requests that the due diligence in the contract be extended a few days to work out additional details. This may include having different contractors come to the house to further evaluate items noted in the inspection report. Having an extension of the due diligence is not uncommon.
If you need more time to complete inspections and be confident in your purchase, then let your agent know that you want an extension. You, the buyer, and the sellers have to agree to extension.