I agree - hysterectomy would be radical. There are plenty of contraceptive options out there - another Mirena, a continuous birth control pill (skip placebo pills), etc.
Hysterectomy causes long-term negative effects even if you keep your ovaries and they do not fail. The uterus and its ligaments are essential to sexual function, natural hormone production, and pelvic integrity (placement of bladder and bowel as well as skeletal alignment of spine, hips, rib cage).
The uterus and ovaries have life long functions.
I had an unnecessary hysterectomy at age 49 - worst day of my life.
I think you've gotten some REALLY good advice regarding the hysterectomy. To undergo a completely unnecessary surgical procedure simply for birth control is far too radical.
Since you are in very good health, have had NO problems with the Mirena and it's obviously working, why fix what isn't broken? Why take ANY unnecessary risks with a surgical procedure?
My advice is have a new device fitted and let nature takes it's course!
I wish you the best
RubyWitch