Is it permissible to pray Duha at 8 AM, and is it true that whoever starts praying it is not allowed to stop?

The time for Duha prayer begins when the sun has risen to the height of a spear and ends just before zawal (midday). Its exact time cannot be determined by a specific clock time, as it varies with time and place. Duha prayer is a supererogatory act, and performing it consistently is better than abandoning it occasionally, based on the Prophet's (peace be upon him) saying: "The most beloved of deeds to Allah are those that are most consistent, even if they are few," and his saying: "Undertake deeds that you are capable of," and because the Prophet (peace be upon him) "would establish a deed when he performed it."