I wouldn't recommend using the same API key again.
If you generate another API key at the same exchange you could contact Gunthar to add another API key. He allows more than one API key at the same exchange.
I have one Bittrex API key for BTC pairs and one Bittrex API key for ETH pairs. e.g. BTC-OMG on one API key and ETH-OMG on another API key to make sure the bot doesn't get confused with the pile of OMG. (So I have two piles of OMG).