Is the 125ml difference worth the exchange?

I do not think that this increase in volume will give you long term happiness, as the liklihood of you needing a revision from THIS revision is around 100%. The weight of these larger implants on your 5' 5'' 140 pound frame will likely cause soft tissue stretch and implant malposition and within a few years, you will need a pocket revision/implant exchange/mastopexy revision. There is nothing wrong with large implants provided that you are aware of the repercussions associated with them. 

Thank you for the question.  Although it is not possible to provide you with definitive advice without an in person evaluation, most patients need more than a 125 cc increase in breast implant volume to see a noticeable difference with revisionary breast surgery.  What I cannot tell you is whether the 125 cc is the "correct" volume necessary to achieve your desired outcome. Sometimes during this type of revisionary surgery, adjustment of the breast implant capsules is also necessary to achieve the desired outcome.  In other words, there may be many variables, besides breast implant volume, to come into play when it comes to achieving a specific patient's desired outcome.Whether or not to proceed with revisionary breast surgery: generally speaking, I advise patients to carefully consider their degree of concern with the outcome of the initial breast surgery and weigh these concerns against the potential risks/complications associated with the planned revisionary breast surgery.   For example, if the patient is concerned about her breast appearance on a daily or frequent basis, it is likely that revisionary surgery will be helpful when it comes to improving her quality of life.  On the other hand, if the patient's degree of concern seems minor and/or she is  infrequently concerned, I would recommend against revisionary breast surgery.
 Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery (regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural” or "D or DD cup” or "much of a difference" etc may mean different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery ( after the use of temporary intraoperative sizers). Viewing the patient's chest wall in the upright and supine positions, with temporary sizes in place, help select the best breast implant size/profile for the specific patient.
I hope this helps. Best wishes.

I am not a fan of larger implants those being over 500 cc’s because of the long term sagging sssociated with them.  If you already have a nice result why spend the money and take risks even though the risks are small?