It depends on your relationship with that person. For some of my relationships it is perfectly normal to return a call two months later. In general it helps i

It depends on your relationship with that person. For some of my relationships it is perfectly normal to return a call two months later. In general it helps if you're clear about it. I have a friend with two cellphones, and she never answers either of them. I know this, and just e-mail her instead (which does get a quick response). I tell my co-workers I only read e-mail once in the morning, and they will have to walk to my office or call me if they have something more urgent (this is quite different from company culture). Etc.