No absolutely not. You are running a huge risk by keeping your funds on a exchange.
You have no control of you funds, you are basically praying that the exchange is honest and is not being hacked.
+ Plus you will not benefit from minting.
There have been so many security breaches the last 3 month:
Mt.Gox
Vircurex
Cryptorush
BIPS
To mention some..
You know the story about Mt.gox, but read theese:
https://bitcointalk.org/index.php?topic=49383.1060
https://bitcointalk.org/index.php?topic=431099.1020
https://bitcointalk.org/index.php?topic=252308.140
Personally - I only put small amount on the exchange always less than 0.5 worth of BTC, and always less than 1 hour.
This.
Coins that are not in your wallet , are not your coins , you practically lend them based on trust.
But I can check my found every 20 days there? Right?