Well, comics take a lot of time and effort to make, so any delay is reasonable.
Take for instance, I make 4 comics every week. However, I've been in the hospital and in recovery for the past three weeks.
So for almost a month, I've been incapacitated, so comics are just not possible until I feel better. This happens a lot, especially since comics on Tapastic are often done during free time. So, no free time = no comic. That's just how things are.
Plus, sometimes we're just not inspired to create anything for a moment, so we try to do other things to bring back that spark. Also, time away from a project can help you think about it better.
Or sometimes, we just need a break.