I'd say it could take you a couple of evenings to get the hang of the place. By that time, you will likely either be addicted or bored
As a Macau addict, I find 5 nights is good, but the problem is what to do during the day time. Take-out lounge girls, or we chat connections (exceptionally easy in Macau) are good solutions if, like me, you are not a gambler. If you like gambling, the casinos are happy to take your money 24 hours per day.
One solution that you might find acceptable is to plan a weeklong trip to HK, and then travel to Macau by ferry as many times as you like during that time. Although it might seem like a lot of trouble to take the ferry each day, I must say it is very easy. I find the time is good for reflection and planning, or snoozing. A typical day might be: wake up in HK, punt or see the sights in HK during the noon/afternoon. Take 6pm ferry from Shun Tak, buying a package (which makes the ferry ride free). Arrive Macau 7pm, clear customs in 5 minutes. Walk/taxi to favorite sauna. Be in sauna by 7:30pm. Stay for 4 - 6 hours. Take ferry back to HK. Sleep.
If doing this kind of thing, a great hotel to stay at is the Bauhinia Hotel, which is right opposite Shun Tak in Hong Kong. Reasonably priced, and you can essentially fall out of the ferry and into bed.
One downside of this approach: No hotel room in Macau to take take-out girls to.
So, some kind of HK/Macau hybrid might make the most sense. A few days in HK, then a few in Macau.
Gherk