Welcome!!! I, too, started out with v2cigs. I really liked them as well! My favorite was cherry. Honestly, I did not care for the flavors of Vapor4life. I tried several flavors, and they all tasted way too strong to me. I now make my own nicjuice, but prior to making my own I used only v2cigs cherry 12mg. I realize there are cheaper places to order from, but I really did like v2cigs. In fact, I still use only v2cigs cartomizers even though I make my own juice. I just refill the carto with my homemade juice when the cherry runs dry.
You asked how long you can reuse a carto: for me, it depends. I have been using my current carto for 9 days. Some people claim to have gotten upwards of 30 days of use out of a single carto. They are easy to clean out and reuse. Take some hot water in a 30mL syringe, and push the water from the vaping end out through the battery side of the carto. I usually run about 150mL of water through it, blow the excess water out, and let sit over night. Good to go the next morning!
There are tons of options out there for vaping. Stick to what you feel comfortable with. Don't get too overwhelmed with all of it. Read the forums, and you will be amazed at how much you will learn. You will be a vaping pro in no time!
Keep up the good work-- happy vaping!!