How long are these separated abs going to last?

I just had my 3rd baby back in October, I've had three homebirths. All of my babies have been born between 40-41.5 weeks. I have really noticed this time that my abdominal muscles are quite a bit more separated than I have ever remembered from the postpartum after my last pregnancies.

When I am "relaxed" the space is a little larger than 4 fingers wide...(maybe 3 inches) when I do a crunch, the space decreases substantially when the muscle is contracted (perhaps down to 3/4-1 inch).

I am about 5 1/2 months post partum, at this point my stomach is still looking like I am a 3-4 months pregnant to me. Not that I would expect it to go back to what I was prior to pregnancy . It does seem about twice as bad as my last pregnancy, so I am wondering if this gets progressively worse each time?

The last time I saw my midwife was at 4 weeks (so it's not like I had a lot of expectations for a flatter stomach at that point anyhow).

Any thoughts on ab separation and what I might do to help return closer to normal? For a long time they actually were sore. They still ache sometimes.