What is the ruling on increasing sleep beyond the amount I swore to adhere to, and do I have to offer an expiation for breaking an oath?

Frequent oath-taking is not a legitimate means of disciplining oneself or striving against one's desires, because it places the Muslim in a difficult situation and may lead to failing to uphold the oath, whereas Allah has commanded us to guard our oaths. If you break your oath, a single expiation for the oath becomes obligatory upon you, whether or not you implement the self-imposed punishments you set for yourself. You are not required to adhere to those punishments. Oaths are dissolved simply by breaking them, and the expiation does not repeat unless you intend for it to repeat. Violating an oath due to being overcome by one's desires does not prevent the breaking of the oath nor does it waive the expiation. As for forgetting an oath, the one who forgets does not break the oath according to the majority of scholars.