If EA is eventually convicted of murder, he will get life in prison or the DP, Imo. No murder that begins in the trunk of a car is anything less than first-degree and/or felony kidnapping (jmo).
Time passing does help "no body" cases, as Steve said. The increasing length of time a person is missing without financial activity, contact to any loved ones, verified sightings, etc can be used to help build a murder case. If indeed LE has a quantity of Christina's blood, that is a huge factor toward an eventual murder charge. And they don't have to rush with charges, he isn't going anywhere and LE can continue to hope she will be found in the meantime. But LE stating in court that they believe EA killed Christina was very eye-opening for me, as far as adding to my belief that they have solid forensics. They don't need a motive and we may never get the satisfaction of knowing what went on in those very few minutes before his car left that garage.
I see EA riding this out, proclaiming his innocence, possibly right to death row. Not all murderers confess, even for a plea. Sometimes, Imo, they just can't/won't admit their crime. Maybe he will get a chance for LWOP if he tells where Christina is...but it would not shock me if he refuses. I can see him playing the wronged victim all the way.
All Jmo, obviously.