Health boost effect

I got on cheats and typed /effect (playername) 21 180 9

What I expected to happen was...:
I was going to have 30 Hearts for my survival

What actually happened was...:
every 30 seconds my hearts went back to 10

Steps to Reproduce:
1.type /effect (playername) 21=Health boost 180=3 minutes 9=20 more hearts
2. Once i got my effect I was drinking health potions
3. once every 30 seconds my heart returns to 10