What are the chances and risks of implants bottoming out a 2nd time?

Usually
bottoming out occurs more with saline implants or if it is from overdissection
of the inframmamary fold, this is difficult to correct. The chances of it
re-occurring, especially with a large implant, it is not insignificant. I would
recommend changing implants from saline to silicone, or a smaller size implant
and fixation to a new inframmamary fold.

Unfortunately,
you have not provided your pre-operative photographs. Most likely your implants were centered
underneath the areola. When this is done
the implants are often too low and extrude from the inferior lateral edge of
the pectoralis major muscle. If the implants
are placed in front of the muscle, the same thing will happen again because
there is inadequate support. I recommend
a new technique called Implant Exchange with Mini Ultimate Breast LiftTM. Using only a circumareola incision it is
possible to reshape your breast tissue creating upper pole fullness, elevate
them higher on the chest wall and more medial to increase your cleavage. Through the same incision, your implants can
be exchanged. Aligning the areola,
breast tissue and implant over the bony prominence of the chest wall maximizes
anterior projection with a minimal size implant. Small round textured silicone gel implants
placed retro-pectoral look and feel more natural, are more stable, less likely
to ripple or have complications needing revision. Implant profile is irrelevant in the
retro-pectoral position since the muscle compresses it. This technique avoids the ugly vertical
scars, maintains nipple sensation and the ability to breast feed. Best Wishes,Gary Horndeski, M.D.

 Generally speaking, there are many advantages of having breast implants in the submuscular position; I would be worried that if you convert your current breast implants to the sub glandular position, you will be exposed to additional problems. Instead, the use of capsulorraphy techniques and acellular dermal matrix as additional support may be indicated. Best wishes.