No as far as I know. I use tracfone and just buy minutes(60 on up) and that gives you 3 months or a year air time usage.. they come together on the purchase.. you need airtime usage(months) and minutes. They come together and will tell you right on the phone when your on the main page what they are now... like 300 min service ends 1/23/2012 so you have to buy more airtime/minutes by then, They come together Hope that explains it from my point of view. There is a Tracfone forum on Fat Wallet or just google for info.
Like PP said "airtime" usage is how many days/months of service you received with your "minutes". Purchasing 60 "minutes" gets you 90 days of "airtime" usage (service).
The easiest way to do this, is buy a year card (airtime) and it comes with 450 (or double minutes and there are always bonus minutes) so you get a year of service with 650 or more minutes. We use it and it's a great deal (unless you have a teenage texter!)
As others have said, if you add a 60 card thats 60 minutes of talking time. The only potentially confusing thing is 'texting'. Sending or receiving a text is .3 minutes. So talking... 1=1. Texting is just a portion of a minute.