“The market can stay irrational longer than you can stay solvent.”
The market can stay irrational longer than you can stay solvent.
  股市保持非理性的時間, 要比保持破產的時間長。


The first part is okay (although there is no Chinese word meaning "can" or "able to"), but in the second part 保持破產 = "maintain bankruptcy" = "remain bankrupt" is the opposite of what the quote says.  (Also, it might not be a Keynes quote.)

The grammar structure 比...长 is also not the closest possible match to the English, so I wouldn't use it (even though it's correct).

Anyway, let's see how it's translated online:


  市场保持非理性的时间可以长到令你破产。
  -- 凯恩斯
  克纳普，理性的股票投资, 2013；Google Books (screenshot)


The last part above 长到令你破产 is something like "extends until you go bankrupt".  I think 市场 = "market" is more general than 股市 = "stock market" (I believe shorthand for 股票市场); maybe 股市 is more precise.


  基本面保持非理性的时间可能会超过你能够保持清偿能力的时间。
  财富, 2009; Google Books


Here 超过 = "exceed" and 清偿能力 = "solvency" are suitable.  However, I feel the 可能 = "possibly" feels wrong (the quote does not say "possibly longer", just "longer").  Also, having both 能够 and 能力 seems excessive.  [I'm not sure what 基本面 is doing at the start here.]


  市场保持非理性状态的时间可能超过你保持清偿能力的时间。
  CReaders.net


Here 状态 is used to mean "state" (as in "a state of irrationality").  I don't think it's needed.

Combining these ideas, I suggest:


  股市能保持非理性的时间超过你保持清偿能力的时间。
  My direct translation: The stock market can maintain irrationality time exceeds your maintain solvency time.
  Google Translate: The stock market can remain irrational longer than you can maintain solvency.