Here's my take on it, since you asked:
For cash,
1) determine how much you want held in cash (day to day purchases, emergency money, one off expense, upcoming holiday, asset allocation etc), then
2) hold it in the currency in which you plan to spend (invest) it.
eg If you had SEK1000 of expenses coming up in August and you made the decision that would incur this cost today based on the information you have then my advice would be to convert the money to SEK now instead of exposing yourself to the currency risk, even if you had a view on what the market would do.
In your case, if you are planning on doing something with it that requires NOK then by all means keep it in NOK.* Otherwise bite the bullet and convert it to whichever currency you need it in**
* And there might be a few options here! The OBX might have some bargains for starters. Alternatively, you might want to convert it to USD and buy the Vanguard energy ETF.
** The one big exception to the rule is if you are a US citizen and the US doesn't know about the account in Oslo (which is illegal, btw). Then there might be a case for keeping it that way but YMMV.