My husband requests that I stay up late at night with him but I refuse because I want to pray the night prayer, so I sleep early. Is this (refusal of mine) disobedience to a husband?
It is incumbent upon you to obey your husband in good. If he calls you to stay up late and you will definitely fail to perform the fajr salaah at its fixed time or (he calls you to stay up late) to watch what is evil, then you do not obey him. As for other than this then it is obligatory to obey him even if the night prayer is missed because it is an (optional) Sunnah and obedience to a husband is obligatory.
وصلى الله على نبينا محمد واله وصحبه وسلم
[Source: Fataawaa Al-Lajna Ad-Daa-imah 19/222]