Programming hot water on twice per day, or leaving it on all time, makes little difference on energy saving.
A modern unvented hot water cylinder (white hot water storage tank normally in upstairs airing cupboard) is very energy efficient. That means, it has very little heat loss while storing hot water. It is also not as warm as before in the airing cupboard compared with an old type of hot water cylinder.
When hot water temperature reaches 60C to 65C degree inside the cylinder, the boiler stops heating hot water, no energy is wasted even you put longer hot water on time.
Total amount of energy used for hot water is determined by how much hot water your family has consumed, not by the on and off time.