In our R&D shop our experience is with the MistAway units. One is mounted on a 4020 Fadal and the other on a DMG DMU 50 5-axis machine.
The unit on the Fadal has been in service for a year and a half. Given the interior volume of the machine, it is operating near the manufacturers stated limits of effectiveness. Overall performance has been satisfactory - keeps the mist down and reduces the residual coolant on the walls and roof of the machine (has the top enclosure sheetmetal). As yet we have not had to replace the filters - two of them can be cleaned and reused, the third final filter needs to be replaced. Admittedly, we do not run 24/7; more like 8/5. Given the Fadal's accessory plugs that respond to M codes, we've gone to running the unit only when the coolant is on.
The DMU 50 is a much smaller and tightly sealed volume, so the unit mounted on it is very effective (in service for ~8mos.). Before we installed the MistAway, at the end of 15-20min machining cycle the 'fog' inside was rather unpleasant if you opened the door immediately. Now, not a problem. A further benefit is during machining - we now have a much better view of machining as its taking place since the mist inside is dramatically reduced.
The units themselves were easy to install - prepping the DMU however was quite a 'story'
The main shop has a Royal unit of the Filtermist type. It's effectiveness is compromised by being used with open-top machines and some lengthy plumbing, but it has mitigated the mist problem satisfactorily. Certainly, installation and servicing are more involved.
Don't know the cost of the Royal unit, but believe the MistAway enjoys a pricing advantage that helps offset the filter cost. HTH
Fred
PS Was just going to hit SEND when other fellow in the shop came in and said ' Uh, looks like we ought to clean the filters (on the Fadal unit)'. The filter indicator was near the top end of the blue or acceptable zone. Based on that, I'd say the manufactures recommendations are reasonable - 4-6mos. for a machine running near continuously and 1yr. for 8hr a day operation. BTW, we use a Blaser coolant: BC20. Damn, now I have to go clean filters