When is Freight earned?

In international trades, freight is usually paid in US dollars but when trading with certain areas (eg Libya) it could be euros; certain trades (eg sugar charters from East Africa to UK), use British sterling; coastal trades use local currency. Unless there is anything in the charterparty to the contrary, freight is earned on completion of the voyage when the cargo is delivered in merchantable condition. However, in dry cargo, it is common to see such clauses as freight deemed earned upon loading, discountless and non-returnable cargo and/or vessel lost or not lost as loaded on board. Effectively the question to be asked is who has the risk of losing their freight in the above terms, the owner or the charterer? In the first case (on delivery) the carrier risks forfeiting the freight if the cargo is not delivered therefore the owner would be prudent to insure against that risk. By contrast in the latter two cases the charterer having paid the freight, perhaps even before the ship has sailed, is at risk and should take out insurance.