I never had much luck with Prevacid. Nexium works better on my tummy. Nexium works longer than the other PPIs I tried. Even "24-hour" didn't make any difference. I think the dose was just time-released and less was available when I needed it most - before breakfast.
Timing is critical! I only get relief if I take it 1/2 hour before eating breakfast. And it's extremely important to eat a light breakfast! The stomach's acid pumps are not available to be turned off if you don't eat something.
I've never had your dose, but I did need it twice a day just before Nissen (Toupet) surgery. The second dose didn't really help much.
I always could tell the first dose helped. The second and third day there was major relief in the morning. Just before getting surgery - giant PEH - stomach stuck in chest with valve wide
open - there was only partial relief. Going through months of testing was awful.