Can say for sure you don't want to take a dry "hit". Have done it once or twice. Cotton burning doesn't taste too well.I sure don't want to burn my cotton, or waste the juices I mix with high settings.
Using mech mods I usually don't use more than ~ 24 Watts average. If you're using a regulated device it's okay to use higher wattage.
Increased wattage doesn't necessarily increased heat. If you take long draws you might increase the heat. By long I mean 10 seconds or more.
Usually do about 2-5 seconds drawing myself. That doesn't effect how much juice is consumed directly. It does but not as in anything I've measured to say accurately.
I use 4-6 ml of juice per day between 3-5 different mods. At one time I was using only 2 ml per day. I got more gear, got into RDAs. More is used with different gear over tanks.
I still don't feel terribly concerned over my consumption rate. Know quite a few that use 10 - 20 ml of juice a day, and some using more. If you do a bit of DIY then cost isn't much of an issue.
Best place for buying flavors to mix is BCF, bar none. They got decent prices and offer sample bottles of 10 ml to try for less than $3, and 10 ml of flavor can stretch a bit. You might pay a bit more for a 30 ml of flavor but even then BCF still has good prices. Their flavors are top notch quality too.