Brain wallets are easily guessable, you should move your funds into something else immediately.
Off-topic I know, but this seems to me to be a complete myth.
Chosen at random from my old Longman's Dictionary (pages opened at random)...deform lockage sedate daunt captive
The dictionary has 70,000 words:
70,000^5 = ~ 2*10^24
Try brute-forcing that
Well you have solved only half the problem. For most people, a set of words that can be reliably memorized is going to be easy to brute force.
Choose words from different languages.