just make sure the phone is "unlocked" from the OEM sim and the original carrier
so that it will work with whatever sim you purchase
tmobile pay as you go, you buy the $$/minutes you want
other carriers you buy by the Month
a $39 month of unlimited minutes, is probably a better buy than say $20 worth of minutes that you will burn thru in a few busy days..if you need many calls and have to sit on hold
PCS metro.. or maybe consumer cellular ?
and yes after months of non use, it will cease to be valid and you will need a new card and number
time span varies with carrier, most expire after 90 ~ 180 days
so the carriers and can recycle the phone# and clear the account