What is the ruling on making frequent covenants of obedience to oneself, such as a Muslim covenanting with his Lord to perform a specific act of obedience for a set period and then renewing this covenant after its expiration? And is frequent covenanting considered disliked?

These covenants are treated like oaths, and their proliferation is disliked for fear of dereliction and failure to pay expiation. You are required to pay expiation for an oath if you break it. The reprehensibility of this proliferation is determined by custom, and scholars have not set a specific limit for it. Therefore, you should encourage yourself to do good deeds through other means than such covenants, and not to multiply them for fear of breaking them and the dislike of frequent swearing.