Split testing is not (or should not be) a one-time thing!
If you got good results after you split-tested something, it doesn’t mean you should stop.
Improving your open rates just by 1% can bring a lot of revenue in the long run, so why leave it at that after getting results just once?
You can read more about that in my book here: https://www.amazon.com/Ecommerce-Email-Marketing-Playbook-Business-ebook/dp/B09X8G5T8F