I never buy it and have yet to need it. Some people always buy it.
If you can spend the money and are concerned, go for it. If you have to sacrifice the quality of machine you can afford it may not be of better value for you to purchase it.
Buy a 27" refurb. Put 16gb or 24gb of RAM in it. Also drop a SSD in it.
I have purchased multiple refurb macs and they have all been great experiences! Don't use a HDD or a Fusion Drive. They both have moving parts and are at a higher risk for failure. As far as SSD, the Samsung Evo 849 series has an incredibly low fail rate.