Well, I'm guessing you already know that juice consumption is highly personal - some folks use 2 ml a day and others go through upwards of 10 ml - so there's that. Really, then, your question is about what the change is in going the RDA route.
I think the biggest factor is the build, not a change in your habits (I drip vape at the same rate as I used to use clearos), and that comes down to number of coils and the resistance (and the resultant power used). With dual coils running net .5ohms on a mech (reo), I'm looking at going through about 1.75 times as much juice as I was with single 1.5ohm coil clearos at 10 watts. If you're already running either dual coil clearos or subohm coils (e.g., the Atlantis, especially at higher power), you won't notice so much of a difference.
Now, you could run single coil builds with the same resistance as you use now and prolly not notice any difference at all (after you settle down from the "OMG, this tastes sooooo much better" phase).