My question was about what happened during your warranty period. nrp's response was independent of warranty obligations.
They just offered free batteries.
The issue did not arise until after the warranty period expired. The manufacturing flaw drained the real-time clock battery which lasted about a year. Their first fix was to send a new battery; the second fix was a soldering job. I am not a lawyer, but this does not seem like it is legal. The manufacturing flaw was present from the beginning but was masked by the battery's charge.