I hear you there Mike,
I'm going to be looking at the same thing after Christmas as I have a LOT of actual cutting work to do and have to stay within resonable lead times
It's worse with the bigger machine I'm buying as RF tubes cost £1500 to £3000 to get refilled when they go down, a second tube for a quick swap out isn't really very practical at £7000+ each either
Getting that finite balance is hard but the savings available if we do are well worth looking for.
At the minute I tend to opt for 85% power max and keep a spare tube in stock.