I've foolishly left my coins on an online exchange far too long. The closing of BTC-e.com convinced me enough to 'evacuate' my crypto from Bittrex before it is too late.
It's not that I have something against Bittrex. But let's face it: it is an online exchange and in the last few years we've seen that those places aren't very secure to store your coins long-term to put it mildly. A prime example is Mt.Gox; this online exchange went bankrupt and lost hundreds of thousands of Bitcoin, leaving many users of Mt.Gox financially devestated. Another example of an exchange going down in flames is Cryptsy. Recently, the site BTC-e.com went offline as the domain name got seized by US authorities due to a suspected widespread international money laundering.
I was active on BTC-e for years but luckily only had 287 satoshi left on the site when it was taken down. However, I know some people who had crypto worth several thousands of USD left on the site and they are not amused to say the least. Scenario's like mentioned above could happen to any online exchange. I've neglected the aspect of security for too long now and decided to set up an Electrum wallet. It may not be the holy grail regarding security but it surely beats any exchange ;)