Exactly how much does somebody have to be drinking to suffer withdrawal symptoms?

A friend of mine recently informed me that some people who quit drinking cold turkey can have withdrawals so bad they suffer siezures or even die.

This blows my mind, because back in my twenties me and my friends would drink every night for months straight, usually between 5-15 a piece depending on the occasion. I quit cold turkey from that amount for about a month probably a dozen times and I never had withdrawal symptoms of any sort. In 2007 I think I drank every night for a year straight.

Am I just insanely lucky to be alive or do some people drink even more than that? I’m male and was about 240 lbs at the time if that’s relevant.