First off I should point out that your battery is safe to leave on at all times (as in not engaging the 5 click manual off function) as long as you aren't carrying it in a pocket or a purse, etc... The button is what completes the circuit. It's not going to randomly explode in the night. The only way batteries can explode is through heat, physical damage, or overcharging (which is protected by a circuit anyway which VERY RARELY (like far less than 1 in a million) fails) and usually only when charging. Lithium Ion batteries are in just about every modern portable electronic device from cell phones, to tablets, to laptops. If they were randomly exploding all the time then you'd hear about it. You don't, because it doesn't happen. There is no need for superstition. The only reason you need to use the 5 click manual off mode is if you are carrying it in your pocket or purse as pressing that button for long periods of time can strain your battery, kill your atomizer, and drain your battery's charge. Pressing the button with no atomizer (or cartridge in your case) on it is not good at all for your battery. Don't do that.
You don't have to take anything apart if you don't want to, but if you do you'd best put the cap back on because juice exposed to air isn't great for it, in both the nicotine potency or the flavor department. If you want a crash course on the specifics of batteries please read my blog, the Vaper's Handbook:
http://www.e-cigarette-forum.com/forum/blogs/shoganinja/2998-vapers-handbook.html
More importantly I'd look into finding replacements for those antiquated cartridges. There's some good advice concerning that in my blog as well. No offense, but there's a reason they give those away in starter kits.