No, definitely don't express yet - probably unlikely to cause a problem, but not worth the risk!
In my first pregnancy I leaked from 16 weeks, and eventually had to start wearing breast pads to soak it up, can't remember at what point, though. My milk production was ridiculous - I ended up having to exclusively express due to problems my son had with latching, due to an undiagnosed lip tie, and I ended up with a freezer (well, actually 3 freezers - mine, my parents and my in-laws') full of stored expressed milk! I was a little obsessive and kept a record of the volumes I pumped and how much Hayden drank, and at my peak I was expressing 3 times the amount he was drinking! Wouldn't recommend it, though - I ended up with a breast abcess which had to be drained multiple times due to my crazy over supply. That was a bit of a wake-up call and I realised that it had got out of hand. When you breast feed your baby regulates your supply and I wasn't doing that properly, but it did show me what my breasts were capable of!
Anyway, this time I noticed leaking quite a bit later, probably about 28 weeks, and it's not so much. But I have GD, so now that I am 37 weeks I have started hand expressing colostrum to freeze and take to hospital with me in case baby needs top ups to treat low blood sugar after she is born. I am getting a pretty respectable 5-10ml a time. I won't store too much, though - remember you only produce colostrum for a few days after baby is born, then it changes to mature milk, and this happens for a reason - I won't need much colostrum because I won't need it for long.
So to answer your question, yes it might mean you will be a fantastic milk producer - in my experience it did - but we are all different, so who knows
