I'll be doing another reduction. Should I do scar therapy so the surgeon can have the most healed skin to work with? (photos)

Your surgeon will be cutting out the scar anyway, so it won't make much of a difference. I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with. Finally, make sure your surgeon is a Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS).
Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified, Double Fellowship-Trained Beverly Hills Plastic Surgeon

As scars mature over months to a year (from bright red to purple-y red to dull dark red), the quality of the scar usually improves.  There is almost always lightening of the scars. Silicone sheets, Mederma, and Bicorneum are reasonable and popular options. I recommend that the scar therapy begin after the scars have healed and there are no open areas, which usually takes 4 - 6 weeks.Kenneth Hughes, MD, ABPS Board Certified Plastic SurgeonLos Angeles, CA

The technique I recommend is The Bellesoma Method.  This will reduce and reshape your breast tissue creating upper pole fullness without implants, elevate them higher on the chest wall and more medial to increase your cleavage.  The weight of the breast is transferred to the underlying pectoralis major muscle resulting in pain relief and long term stability.  Vertical scars are avoided, nipple sensation and the ability to breast feed are maintained, if not injured during your previous surgery.Best Wishes,Gary Horndeski, M.D.

your result looks good except for the darkness around the vertical scar.  This is simple to revise and can be done under local anesthesia.  As far as scar creams are concerned follow your surgeons advise on this. I might or make not make any difference.

Dear annyriverrose,
I understand you are concerned with the appearance of your scars. As your scars heal, it should flatten out and lighten. Loss of pigmentation or hyperpigmentation may also be experienced but will resolve over time. Always follow your surgeon's post operative care instructions when it comes to scar management to avoid any complications like infection and for faster healing and recovery. You should wait at least 6 months and at that point your scar should be well mature. 
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Thanks for your question. It looks like the vertical scar still contains some of the darker pigmented skin from your areola. So, I don't think any particular scar therapy is going to make a difference at this point. However, at your next surgery, I bet your surgeon can remove that darker skin and get things looking much prettier. At that point I'd get your surgeon's advice on scar care. Best wishes