This kinda is the case for everyting that comes out. Old producs outlast the new one all the times, unfortunately

Pretty sure it isnt, but thats the case for almost anything made today.

I cant rly give you an answer since i bought it only 2 years ago.

For now it seems fine, looks the same as new, no scratches or worn down rubber. Tho the cable is kinda thin and not braided so im pretty sure that will be the point of failure (tho i dont mind, i have done it on the original one a couple of times)

My mouse hand was moulded by MX518's shape so getting a new one with the same shape felt great

you should know that Logitech revived the series, you can still find them under the name "G MX518"

I was in the same place as you, first time this mouse started dying i managed to keep it alive for couple more years by changing cables and shit.