i don't think this argument actually makes sense. The rate at which money arrives in people's pockets via income such as wages and becomes available for them to

i don't think this argument actually makes sense. The rate at which money arrives in people's pockets via income such as wages and becomes available for them to spend - what you call the half life of money - is effectively what people think of as money. What money means to most people is the amount available for them to buy stuff with, and while the money may recirculate when they buy something for personal consumption the actual goods and services do not. This means that money recirculating back around faster through wages has the same effect on inflation as just printing and handing out more money: both result in more money chasing the same limited supply of goods and services. When looking at the economy as a whole, it's the rate of flow that matters. This is especially true if you follow MMT. Remember, the whole underlying premise of MMT is that the government's ability to pay for goods and services is not in any way limited by a need to collect money first, that they cannot ever be forced to default on debt denominated in their own currency, that the only actual limiting factor is the actual real resources like labour, raw materials, and so on, and that the purpose of taxation is to keep inflation under control by reducing private demand for those things. From that point of view, money sittting in offshore accounts is a red herring because it doesn't represent consumption of real resources, and wages and money being brought into the country to buy things with are exactly what does need to be taxed because they do represent actual demand which will cause consumption of those resources.