Guys, for all practical purposes.
The battery.
If you look at how an average rider uses the bike, hint if you are putting 30k miles a year on the bike, while that is awesome! especially if you love riding like I do, that does, put you in the heavy use category. not an average user But...
If you do the math, a battery is good for what 2000 - 3000 cycles. At lets say 100 miles a pop. That's 200 thousand miles of riding time before the battery would theoretically drop 20 percent of it's capacity.
How long in reality would that be for you to actually reach that many miles on your bike to hit that threshold for your battery.
Now if there is a design flaw, then yah it might die sooner and a warranty would be good, especially when you look at the past history for that company, but otherwise, most people are never going to get into the range of where their battery is pushing the threshold of being heavily worn. Most Lith battery's are made to last about 8 years now, if you look at the standard warranties that are given for them now.
Extended battery warranty's to 5 years and stuff like that, are mostly manufacturing hype and sales gimmicks, unless you are a very heavy bike rider who actually DOES ride tens of thousands of miles / km per year.
Now with that being said, wow, a 5 year warranty on the entire bike would be a huge thing, because stuff does break from time to time and that is really pushing the outer envelope. The crux might be availability of parts. If, say, your brake handle breaks and you need a new one, and it takes the company 6 months to get it to you, that's not much of a warranty or service now is it? If your bike is spending as much time in the shop as it does on the road, then no warranty is going to 'fix' what it's problems are.
Aaron