Semiconductors tend to fail on what is called the bathtub curve, where there are high levels of failures at the first first, usually within the first 24 hours, then it flattens down and then goes back up. With extended warranties, you are usually buying protection during the time period with the lowest amount of failures.
This isn’t a great graph, but you can see the curve. (Ignore the horizontal lines, they just are place holders.) In actuality, the right hand curve is to the very far right.
(failures)
X
X
X
XX
XXX_______________________________________X
XXXX_____________________________________X
XXXXX___________________________________X
XXXXXXX________________________________X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-------------------------------------------------- (time)
Manufacturers will usually do burn-in tests and test products for 24 hours. Whenever I buy a new electronic toy I’ll play around with it with heavy usage for the first day, making sure that I use all the functions since stores will usually swapt things out with no questions first.
Things with motors are different matters, of course, and anything portable can expect to receive more shocks than desk mounted equipment.
I usually don’t buy the EW, but YMMV.