No not really I regersiter mine in Jan 2012 and just started two days ago. Expiration on mine updates is Mar 19th, 2013.
The Freshest Data (nTag) supported Navionics cards can be activated / registered to 5 separate computers via brief internet connection. So that is the meaning of the 5 registrations of a single card.
The card's contents may be updated dozens of times among those 5 computers. I suppose you could update the card every single day or more (356+) updates but it would not generally be worth doing such frequent updates since it is easily the case that days or even weeks might go by with no content updates (depends on the region, the type of data, etc.). The Navionics World app tells you fast if there are no updates.
Nominally, the one year's worth of Freshest Data updates should be from the first time you activated the card to the first computer the card encountered. At least for the couple dozen cards I've activated, the one year limit on updates seems consistent. However, I have heard (as the early post indicated) that there may be a bit of bonus wiggle room in the time frame. But that seems to be the exception not the rule so if you appear to be getting a longer update eligibility time frame it is not by a great amount. The wiggle room appears to benefit those who activated cards using the older Navonics World app versions... the current (as of late March '12) version 1.0.7 appears to give a consistent time frame of one year for free updates.
If you have any questions about Navionics cards, my company is pleased to hear from you and we will help you out directly or at least point you in the right direction to get an issue resolved. Drop us a line at [email protected]