The Oanda page in the Manual contains this statement:

Code
Asset parameters. The Oanda V20 API does not return rollover rates, so swap and commission must be located on the Oanda website and manually entered in the asset list.


Elsewhere it's pointed out that rollover rates change and some average must be used, implying that we can't just look them up on Oanda's website.

So, the question is: When/how to calculate these rates? And do they need to be re-calculated weekly? Monthly?

Or can we simply use values in AssetsOanda?

Thanks.