I'm trying to break the sessions up to shorter times, I'll give 20 minutes a shot. But once interrupted, it's usually some time before I can get back to reading, sometimes several hours. As for letting the calls go to voicemail. Sometimes I do just that but the nature of my job is that I need to respond quickly. One of my methods of isolation used to be my "office annex" down the hall, a.k.a. men's room, but my cellular service provider improved their coverage in the area and now my cell phones routinely rings even there. Talk about annoying. BTW those calls always go to voicemail.
Michael
