You trusted your plastic surgeon with your looks and your life. I would recommend following his or her post surgical massage protocol.
That being said, in my practice, I do not believe breast massaging will lower implants, nor do I believe it will make them softer. When I was in my residency, I did a personal survey of all my breast augmentation patients. Of those that were willing to massage, half got hard and half stayed soft. Of those who thought breast massage was a waste of time, half got hard and half got soft. Therefore, in a very anecdotal way, I made the decision that breast massaging had nothing to do with whether breasts got soft or not. Hardness of the breast is related to the body's forming a capsule around the implant. If the capsule is thin and fine, your breasts are soft. If the capsule is thick or rigid, your breasts feel hard. This has nothing to do with the breast implant. It has to do with your body's response to a foreign body. These same exact comments can be applied to a pacemaker, artificial hip, or any other foreign device within the human body.
As to whether massaging brings your implants down, this may be true of implants above the muscle. I am not sure because I do not put my implants above the muscle. As far as breast implants below the muscle, I believe proper placement is the key, and if the implants are actually placed too high or they migrate upward, then no degree of massaging will ever assist. I place my implants in the partial subpectoral space, and immediately after surgery, have my patients wear an ace wrap to keep them from migrating upward. I also recommend not wearing a bra for one month after surgery because bras are meant to push breasts upwards, which is exactly the direction you do not want your implants to go in. I believe the ace wrap worn 24/7 except when showering gives more consistent pressure in a downward direction and trumps intermittent massage no matter how often one massages. I believe the higher placed appearance in the early post operative period is due to silicone being displaced upward within the implant covering, and silicone position can be aided in moving downward with the constant pressure from a high positioned ace wrap. Also, the initial space created between the chest wall and the skin at the base of an implant pocket is V-shaped in nature, and the bottom of the implant is bull-nosed (rounded), therefore constant pressure on the implant helps stretch out the V at the bottom of the breast, and that may be the dropping of the implant into the pocket that some surgeons refer to.
With reference to breast massaging to decrease the firmness of hard breasts, that theory first proposed by Tom Cronin, M.D. in 1963 was the best they could come up with in those days, but doesn't hold water today because most hard breasts early on are capsules around an implant, and only in a Baker 4 situation does the implant not move due to capsule strands going out into the breast tissue. Therefore, moving the breast implant around with a hard capsule around it doesn't make it any softer. It just decreases the chance of going from a Baker 3 to a Baker 4.
The problem with hard breasts is one of an immune response and one should treat an immune response with something that modulates (i.e. decreases) some portion of the immune response, and the mechanical manipulation of a breast implant will have little or no effect on decreasing the immune response which is the basis of a capsular contracture.