I sort of get the same thing happening when I look for a job. I have enough specific business related computer experience now that headhunters tend to come to me rather than me going to them. And sometimes I have recruiters calling me for jobs that are in my area, but the recruiter is calling from someplace completely different, and sometimes in a very different timezone, which results in the weird hours of calls that you mention. So when that happens I'll just turn my phone completely off during times when I'm sleeping or don't want to be bothered by it. Usually these recruiters will also email me as well as trying to call, so I don't really worry too much about my voicemail getting full and missing messages.