> 3 months is longer than 108 days ;)
Following the Gregorian calendar (international defacto standard) this statement is always false, never true.
There's no way all these coins are going to be accepted currencies (literally none are, not even Bitcoin). There's no way all these coins will retain long-term value either.
Anyone who joins in on the mining is doing two things: 1) joining in on the pyramid schemes (on which you as miner and cryptocurrency owner depend) 2) adding to more electricity waste.
As for GPUs. Once the shit hits the fan their price will freefall. If their price falls now, they're pretty much worthless. More so because many of them will be abused. GPUs aren't made to be used 24/7. But yeah, you can play games on all your 1080s...