Levemir lasts about 18 hours hence the split dose but we are all different.
Levemir is recommended in general as you can change your dose daily and it reacts well to that whereas others can take days to make a difference.
There are different stronger background insulins that last 24 hours and beyond but your Doctor/specialist should advise.
Please feel free to keep asking questions as there are lots of people on this forum with years and years of experience.
Tony