I usually have a max 3-day window for replies myself, and alert if I won't hit my target. My threads have a poof clause in case a) someone disappears and b) someone didn't actually disappear but returns after a long time and wants to play more. After a week of no posts/contact, threads tend to move forward naturally around that char...The steampunk one gives still-playing folks the option to assume vanished folks have gone to the temp housing or alehouse and also sticks long-missing/return folks in the alehouse if the plot has moved on without them. If that sentence makes sense. Brain is melting after all the copy-pasting. XD
Dreams come in a size too big so we can grow into them.