You will probably get a more technically correct answer out of Brian Lawson, but till he replies, here goes:
Regulating has to do with the action parts. If you look at the action, it looks like a Rube Goldberg device, with little teeny parts. There are pieces of felt in between the the junctions that will get squished over time, so the notes that are played a lot will get squished more and sooner than lesser played notes. This will make the action feel uneven eventually. So regulating is replacing felts and adjusting the action so it's even again. You shouldn't have to do this every year!
Voicing has to do with the hammer felts, which also get pounded down by playing a lot. The notes that get played a lot will start sounding *brighter* than ones that don't, and over time, will sound uneven. There are various techniques that are used to soften up the hardened hammers with needles or harden soft hammers with liquid to even it all back up so all the notes sound the same and sound bright or dark depending on your taste.
A really good book to read is called the Piano Book by Larry Fine. You can get it through Amazon.com or Brookside Press directly. It's not expensive, but it's got a ton of good info about how pianos work, what terms mean, costs, and brands.
I suspect my piano will be tuned twice a year once it's settled in. But that is just the seasonal change here in Portland, Oregon. Other places may only need yearly, some more often. If you have humidity control in your house yours may go longer than mine. My relative humidity inside runs betwee 45 and 55% almost all year.
I have more *habits* than most folks, I'm afraid, because I have a cat that I do NOT want inside the piano. So I close the lid, put the cloth thingy on the keys, close the fallboard, and put on the cover each night. I also work the insides gently with a vacuum brush attachment every other week or so to keep cat hairs and dust out. This may be overkill, but it's a new piano. What the heck!
Topic: Piano Maintenance