Sending belated e-mails

I run into this problem again and again.

You send e-mails regularly between people who are your friends and family. You don't 'expect' e-mails from these people everyday because you realize they have lives of their own and they don't exist to just send you e-mails everyday (hopefully).

So that brings me to my problem. SInce they don't send e-mails back right away I don't feel obligated to do so either. I mean hey I'm a busy person and I don't have the time to send them e-mails all the time either nor do I need to be doing so.

However, that attitude is where the problem lies. I try to send e-mails at appropriate intervals but it almost never seems to happen. I think the biggest reason for my tardiness in sending e-mails is because I want them to be of high quality writing. By that, I mean that I don't want to send a little pithy response back that is like a slap to the face to the person. As a consequence I only send e-mails when I designate an hour or two to actually sit down and send them. So when I do send e-mails I'm going to (modestly) say that the e-mails are of high quality. However, they do end up having about one paragraph in them that is devoted to me explaining why my upkeep of my inbox has been a little less than can be desired.

So then that got me thinking. By sending e-mails at a later date, is that worse than sending a crappy e-mail to a person when you don't really want to talk to them or have the time? Is there etiquette on this sort of thing? Do people tend to get bent out of shape when e-mails don't arrive at supposedly proper times?

I'm sure that in general there are some people who think that but I would like to think that most of my family and friends don't really care when e-mails are sent to them. Either way this is something that I should work on