Individual JWs set dates because 1) it makes them feel good (e.g., proud they have "special knowledge" no one else has) and 2) they can do it for FREE!!! Making predictions doesn't cost anything.
For instance, I remember my one BIL saying around the time of the 2014 RC ("Celebrating 100 Years of Kingdom Rule!") that this system COULDN'T POSSIBLY be around in 5 years. Whelp, it's now 2019, and this summer will be exactly 5 years from when he said this to me and my wife. . . so I guess there's still some time for his prediction to come true! And as noted above, saying this made him feel good ("I'm such a smart JW! I know something everyone else doesn't know") and his prediction cost him nothing. Will he be embarrassed when 2019 comes and goes without anything happening? Nope. Will he lose his shirt financially if nothing happens in 2019? I don't think so.
So next time he makes a bold claim regarding the end of the world again, I think I'm going to call him on it.
I can't do anything about #1 because he's way smarter and more spiritual than I am. But I could do something about #2.
Next time he says "This system can't last another 5 years" I'm going to say "Cool. I'll buy into that. But let's do this: right now, let's go to a lawyer -- I'll pay -- and we'll draw up an agreement that will come due in exactly 5 years. At that time -- since the New System will be here and you won't have any need for the stuff -- I will take possession of your house, everything in your house, your business and all of your bank accounts. How does that sound?"
You think I can get him to sign the agreement? ;)