This is one of the reasons it's good (where possible) to have co-ownership of things like checking accounts. Though my mother is primary owner of her bank account, my sister and I can write checks, move money around as needed without waiting for any permission. My wife had the same arrangement with her father before he died, and it was a life-saver (so to speak).

As far as assets in the estate, the job of the executor is to preserve, as far as possible, the value of the assets at the time of death until they can be disbursed. That means, for example, don't take any intentional action to increase the value of the assets after the date of death, such as moving checking accounts higher yielding to certificates of deposit, etc.