TomTom's lifetime maps:
*Lifetime – this is the useful life of the device, which means the period of time that TomTom continues to support your device with software updates, services, content or accessories. A device will have reached the end of its life when none of these are available any more.
Garmin:
A product’s “useful life” means the period during which the product (a) has sufficient memory capacity and other required technical capabilities to utilize current map data and (b) is capable of operating as intended without major repairs. A product will be deemed to be out of service and its useful life to be ended if no updates have been downloaded for such product for a period of 24 months or more.
Snooper:
This option applies to compatible Snooper product until your product’s useful life expires or Snooper no longer receives map data from Here® Maps, whichever is shorter.
At least Binatone give you a definite term of free map updates - the others are meaningless, really.