Most electronic devices tend to fail early on, or they just go, and go. Most manufacturer's offer a sufficient warranty to last through this initial "burn-in" period. In 34 years, with many dozen units owned, I've only sent two detectors in for repair, and one coil.
I had to send in my Whites 6000 Di Series 3 about 20 years ago as I had it out in below freezing weather, and froze a capacitor. I had to send in a Fisher CZ5 for a power regulator about 5 years ago. The Fisher was covered under warranty as it was only 2 months old. The Whites wasn't covered as it was my fault for not using it within the recommended temperature range. Cost about $140 to fix it. The coil I had to replace was from a Sovereign XS that was just over the warranty period. I had never used the stock coil, and when I went to use it, I found it was defective. Minelab replaced the coil at no charge even though the warranty was expired. It was obvious the coil was still new, and unused.
I buy my detectors based on their performance, and their intended use. The warranty is a secondary consideration.
Get the one you really want, you'll be much happier using that detector, than compromising because of a warranty you might never use.
Hope this helps, and good hunting,
OldeTymer