How long after the 1st Sofwave treatment should the second treatment be performed to see the most improvement?

Thanks for your question. There is quite a bit of variability in terms of when providers repeat a Sofwave treatment. Technically, a single session can continue to show improvement for about 6 months. However, if there is already a plan to do more than one session (due to the existing degree of collagen loss/skin laxity, there is no need to wait an extended period of time.
A recent study of Sofwave for loose skin in the upper arms had the sessions done about 3 weeks apart. Sofwave subsequently got the FDA clearance for this indication as they proved that it provided significant improvement in about 93% of patients.
In my practice we tend to do session #2 at 8 weeks or beyond- it's really up to the client. Thereafter, future maintenance sessions can be done to prevent fine lines and loose skin from recurring. I hope this is helpful to you.