Decoders can fail for a number of reasons:
Many times a decoder can be 'recovered' by doing a 'factory reset' If it is 'dead', the 'investment' is not too great(at least for non-sound decoders). Many decoders can be purchased for under $20, and $12-15 in 'bulk'. With these low prices(decoders were $50-60 back in the mid 90's), the 'warranty' really is not a factor as the mailing/shipping costs can be almost as much as a new decoder! That said, I have had good experiences with Digitrax, NCE, TCS, and Lenz decoders.
Sound decoders can be expensive(typically you are looking at $100) - I have never had one fail and I have QSI/MRC/Digitrax/Soundtraxx decoders. Most sound decoder warranties are typically for about a year, IIRC. I was talking with Zana at Digitrax at a NMRA show and she mentioned that a 'good story' about how you blew the decoder sometimes will extend your warranty!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
There are several reasons why a decoder can fail.
Failure due to manufacturing defects? Absolutely. One brand in particular was known to have an extremely high failure rate.
Warranties? Yes, TCS offers a "Goof Proof" warranty on their decoders. They will replace them free even if the failure is due to user error or miswiring. NCE offers a replacement policy, but not as liberal as TCS's. Sound decoders by SoundTraxx have a limited warranty, as do QSI and ESU.
Overloading a decoder by trying to pull too long a train can cause it to fail.
You would need to perform some research on each decoder manufacturer's web site to see exactly what their warranty is.
A significant investment? $12 for an NCE D13SR when purchased in bulk lots of 10? I don't consider that 'significant.'
The article in the February MR prompted several questions on the subject. I understand that short circuits can cause decoders to go bad, but are there other reasons? Can they be caused by manufacturer defects? Do manufacturers have warranties on the decoders? Decoders can represent a significant investment so I'm curious about whether a situation like this is totally on the consumer or whether there is some recourse for repair or replacement...