Answering your questions...
Always keep them with gas inside, you will have the option to use green gas, propane, and CO2.
For CO2 and propane, use some silicon oil in the mags to keep them sealed. For green gas the only important thing is to leave always gas inside.
Always try to lube your gun that is going to help too... Also buy some O-rings for propane and green gas mags. Look for them in evike (big store in the US) to know what I'm talking about.
And if you can try to have some spare parts is better to fix them than to be buying all the time new mags (is not easy at the beginning to fix them)
Recommendation, buy from 6 to 8 mags if you can. And pay attention to the selling section in this website there is pretty good deals over here. You will save TONS of money buying used, and there is not many problems as electric guns or the problems are really easier to be fixed. If you need more info you can pm me.
Good luck bud!
Last edited by FULLMETAL; November 27th, 2012 at 20:51..