Possible to reduce refractory period after orgasm/ejaculation?

Specifically, No: Refractory periods are going to vary from person to person and by age (longer as you get older). You may be able to achieve your shortest personal refractory time by maintaining a healthy lifestyle (eating right), staying fit (interval training, cardio), and early/vigilant treatment of medical problems (particularly those that affect blood vessels - blood pressure, diabetes, cholesterol, etc.).

Reduce refractory ..: One possibility is to continue the stimulation ( thrusting or touching the penis with the vulva) despite poor or no erection before you feel to go to sleep. Other possibility is to take ssris ( some antidepressants of the family of prozac) 4 hrs before sex to have delayed eyaculation so you dont have to look for two sexual sessions in one night.