It depends on the half-life and the time between doses. For example some opiates with a particularly short half-life (such as hydromorphone) redosing later in the day (like 12 hours later) should yield an equal amount of euphoria as the first dose has had enough time to clear out. Now say you had some morphine which has a longer half-life, and you dose 6 hours after your initial dose. There will be less Euphoria as the first dose is still highly active in one's body.