I wouldnt trust any software wallet again. Just take a look at the bugs electrum had in the span of a year, almost any of those bugs could have led to losing your coins.
Bugs(plural)? 
I'm aware of precisely one major vulnerability that Electrum had recently... no-one noticed it for a long time. Once found and advised, the Electrum Devs fixed it immediately.https://github.com/spesmilo/electrum-docs/blob/master/cve.rst
To be exploited, you needed to be running the insecure version, have the wallet actually open and running AND visit a webpage that exploited the vulnerability.
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If you really want to store your coins safely you will have to buy a hardware wallet.
You do realise that hardware wallets like Trezor and Ledger have had security vulnerabilities too, right?https://blog.trezor.io/details-about-the-security-updates-in-trezor-one-firmware-1-6-2-a3b25b668e98
https://www.ledger.fr/2018/03/20/firmware-1-4-deep-dive-security-fixes/
That isn't to say they aren't one of the safer options, along with paper wallets... people just need to be aware that nothing is 100% secure.