Definitley reinvest it, in an Ether backed token! Why? Many tokens are backed against Ether, meaning they still benefit from the price increase in Ether when you change them back to Fiat.
because it has been created using Ethereum Technologies (erc20) it doesnt mean that it will always increase just like ethereum is doing.
There are a lot of coins that when etherem goes up, those tokens go down too, it is just like a correction. All the coins have their own movements, they are not copying ethereum or whatever you want.
Maybe sometimes they are just following bitcoin, but only because they are following the hype.
Just keep the ethereum that you have, do not sell it.