I'd be curious to see how the 50w compares to a 30w MOPA for dark marking stainless. I can get nice black marks with my 30w but for anything besides small text it's just not cost effective. It takes less time to deep mark than it takes to get a dark black mark. I would really like to see a graphic about 1" x 2" dark marked with a 50w and a 30w MOPA to see how they compare - time wise and quality of mark.

The nice thing about fiber machines is that they have unbelievably long mtbf numbers. You wouldn't really need to have any spare parts on hand, anything that fails would be a fluke and Murphy's Law would ensure you bought the wrong spares anyway... I have had one machine just over two years and the other just over one and have had zero problems with either one and have done no maintenance besides cleaning the dust that settles on them.