Tom, In what proximity to the printer do you place the humidifier? By humidifier, I guess you're speaking about an active, rather than passive, unit.
If this issue of relative humidity is the potent point that it's discussed to be, what don't the printers have built-in humidifiers local to the head assembly? It would make much more engineering sense, in my mind, to put the moisture where it's needed rather than in the entire room around a printer. No? It is the head and, in specific, the piezo nozzles than require the moisture - correct?
Humidity control "near" the head is rather impractical. There are many locations where these printers are sold that have no need for humidity control because they operate in a fairly humid environment. Controlling humidity for ANY inkjet printer will extend it's life. While Canon and HP printers very effectively hide their clogging problems they suffer just as well. After using both I can't say which is cheaper to operate, but I know I don't use much ink any more with my Epson printers once I regulated the humidity in the room. Certainly this would also mean a Canon printer in a similar environment would get much more life out of the head before it fails. So humidity is important.
Personally I decided to install a room humidifier that automatically keeps itself full. I purchased the XXL model with dial controls from Habitat Monitor
. They modify a standard humidifier with a float/fill system. (This wouldn't be difficult to do yourself if you are handy with stuff like this). The supply tube comes from an r/o water unit which extends the life of the wicks. A set of 4 wicks is about $20 from amazon, each wick lasts about 4 months with the r/o water. I also add a little bacteria treatment to the water every week or so.
It has three speed settings for the fan, I use the lowest so it isn't too loud. How much it runs depends on the current humidity. I have in floor heat so my furnace does not dry my air out too much in the winter, but the air conditioning in the summer does dry the air a little. But Utah is a pretty dry environment, so it always runs some. I have a humidity gauge on the opposite side of the room where the printers are and I have the humidifier set to keep that at 45%. The room itself is about 20 feet by 20 feet, but it is open into a hallway so there is no door, and the humidity can escape to the rest of the house. Despite this it can still keep the room regulated without running all of the time.
Works well, not much effort, and I don't spend much time or ink cleaning any longer. Last time I fired up my 4900 (after 4 weeks of non use) a lot of nozzles were missing, but I printed my cleaning page instead of doing a clean, and they all were back. Indicates that some "clogs" are just air getting pulled back in.
One additional item, I've heard maintaining humidity is also good for many of the papers used in these printers as well.