If I were Mistress I would lock my sub's cock in a chastity device and promise to let him out every day. Every day I would promise to give him the orgasm of his life, but it would almost never happen. I would bind his hands behind his back whenever I unlocked his cock cage so he could not touch his own cock. I would give him a bath (or a shower) every day and personally tend to the cleaning of his genitals and cage.
If I were Mistress I would fill my sub's head with fantasies. I would tell him some of his own (with my own evil little twists). I would tell him some of mine and make him think I was going make them all come true. I would tease him with these fantasies every day, just to make him squirm.
If I were Mistress I would tie my sub to the bed and remove his cage. Then I would give him the longest, slowest blow-job he had ever had. I would suck and lick his cock and balls until he begged me not to make him cum. He would know that he had not been locked up long enough for that. I would reassure him that I had no intention of letting him cum, and then continue teasing his cock with my tongue.