Will downsizing help with longevity? Currently 700 cc, considering downsizing.

You need to go smaller. Since your implants have bottomed out, they will do so again, even with mesh. You may need to go down to 500-550 so they will stay up longer. Breasts do not belong under your chin.

Managing bottomed out breast implants is not always easy or straightforward. Each time somebody has revision surgery the chance of having complications or undesirable side effects go up.
Without having access to complete context, we can’t give you yes or no type of answers.
I suggest Patient have a inperson consultation with local plastic surgeons in the community.
The following are some general recommendations for finding the right provider.
Board certification is somewhat irrelevant unless it’s in plastic surgery.
Being board-certified in plastic surgery does not mean somebody has mastered any one single procedure, or is even good at any one single operation. It should be the minimal criteria when beginning provider select.
To find the best provider, I suggest patient schedule multiple in person consultations with experienced plastic surgeons in their community. During each consultation, ask each provider to open up their portfolio and show you their entire collection of before and after pictures of previous patients who have similar body or facial characteristics to your own. An experienced plastic surgeon should have no difficulty showing you the before and after pictures of at least 50 previous patients. An experienced provider should in fact have hundreds or preferably thousands of before and after pictures to choose from for commonly performed procedures.
Being shown a handful of preselected images, representing the best results of a provider’s career is insufficient to get a clear understanding of what average results will look like in the hands of each provider.
There is no correct number of consultations needed to find the best provider. The more consultations you scheduled the more likely you are to find the best provider for your needs.
Take careful notes during each consultation, especially regarding the quantity and quality of before and after pictures. It’s not a bad idea to bring pictures of your own body/face to use as reference when reviewing before and after pictures.
The biggest mistake patients make is scheduling only one consultation without properly vetting or comparing providers before scheduling surgery.
Best,
Mats Hagstrom, MD