I had my right knee replaced in 2013.  My knee was injured from a 1975 downhill skiing accident when I was trying to do a 360.  A month after the surgery my knee was less painful than it was before the surgery.  Seven plus years later my knee is really good.  It is not as good as when I was 24 years old, but we can't expect miracles.  Most people have knee replacement because their knees have become too painful and is adversely affecting their life.  I remember what my surgeon told me.  Before they could do knee replacements people with bad knees had an increased rate of death.  The death was caused by the person becoming very inactive and an associated decline in their health.  As you know the key is doing your rehab religiously and early.

I only had one knee done.  I can only guess how difficult having two knees done at the same time would be.

Good luck and best wishes.