I've been using the Drionic unit (one of the cheaper type of Ionto units) for over a year and a half with success. I pretty much stuck with the 30 min a day routine, till the sweating stops, although sometimes i would stop treatments after several hours worth of treatments and then stop because I was too lazy or didnt have time and after several days (sometimes after 5 days) after my last treatment, my hands would all of a sudden stop sweating. I don't know why, but sometimes it happens that way.
Also, I've never really done maintenence treatments. I basically don't start the treatments again until the sweating starts to come back pretty noticeably. I do this mainly because I'm lazy lol. Sometimes my hands will go for a couple months before sweating starts coming back, sometimes it starts to come back after only a few weeks.
I'm also abit worried that doing treatments too often might reduce the effectiveness of Iontophoresis, which is another reason why I wait long periods before starting my treatments again.