Another vote for the powered respirators
I'm probably preaching to the choir here, but if there is any way you can get one, go for a powered respirator. Like most of you, I've worn lots of different masks, but I never really felt any of them were doing what I wanted... no, actually, what I needed.
I finally picked up a Trend Airshield Pro at a recent woodworking show; but not before walking back to the display a half dozen times. It took me that long to convince myself that I could justify the cost to SWMBO.
I freely admit that the first time I put it on I was concerned about the extra weight, and the sound of the fan (it's quiet, but you still have to deal with bone conduction!) Anyway, I turned it on, felt the gentle flow of air across my face, and within 15 minutes I'd forgotten I was wearing it; and I haven't looked back since. The weight is well distributed no matter your head angle, and the fan is quiet enough that you can still hear the sounds of the tool on the wood.
To date, the longest single session that I've worn mine for was about 4 1/2 hours, and that was no problem. I also wear it for flatwork when I'm going to kick up a lot of dust, and it is great there as well. Also, if you need to wear eyeglasses, like I do for close-up work, they fit easily within the mask.
As far as cost goes, that's really relative, isn't it. Example: If you wear this particular respirator an average of 10 hours a week, after a year that's about 50 cents an hour; over two years it's about two bits. So for less than a single Starbucks coffee a week, you can have healthier lungs, and hopefully continue doing what you enjoy doing for that much longer. When I look around my shop, I see lots of tools that, at the time of purchase anyway, seemed "indispensable", but which are now collecting dust; enough tools to purchase more than a few powered respirators! Does that sound like anyone you know?
Last thoughts. I would also suggest that a respirator should/must be used with a dust collection system, and not in place of one. By the way, I'm not trying to recommend the Trend ahead of any other brand (although I do like mine); I am, however, recommending that you strongly consider getting a similar unit of some kind; any of the popular brands should be worth a look.
Sorry if I rambled on.