I agree that loss-of-enthusiasm can be a problem. As a compromise, would it be possible to put up a "teaser post" a day or two ahead of the real plot details, giving the approximate time that important information will be revealed? That way busy muns would know something is happening, and may be able to check in briefly, so they won't be quite so behind the next evening.

I'm not sure why an impending event would cause people to tag less, especially since with or without an announcement we tend to know approximately when experiments are going to happen.

As for backtagging, while I find most people are happy to continue a thread for weeks, starting one more than a couple of days after it should have happened generally seems to be less well-received.