isn't vaping 3ml comparable to smoking about one pack of cigs?
Not really. Nicotine absorption through vaping is severely hampered - molecule sizes

.
I have some days where I'll go through 2-3ml (one aga-t2 tank) and another where I'll gove throuh 8-10ml. When I first started, it was 10-15ml a day. I don't really care about how much, just as long as I avoid Nic OD symptoms (headaces, shakes) and I stay off the analogs.
How often I vape really depends on the flavor of the juice. I had one called Blackberry cheesecake that I went through 30ml in about a week.
I have no regrets... except that I'm out of blackberry cheescake

.