I was playing through all the Lemmings Revolution levels and eventually quit playing. A month later, I went back to the game completely wondering why I stopped playing and remembered. The later levels require you to time your solutions in such a way that the Lemmings can pass a certain spot at a certain time, but all the while it needs to be done within the level's time limit.
An example is the very very last level, appropriately titled "It's Going to Take Time." In this level, at the very end, is a rotating log with spikes on it that moves ever-so-slowly and only cycles twice throughout the levels' time limit. For half of its cycle, it's down by the ground where the Lemmings walk, and the other half of the cycle it's up in the air so the Lemmings can walk under it. The rest of the level is a multi-layered puzzle filled with one-way walls, switch-driven platforms and even a bit of backtracking. I liked the level in and of itself, though upon reaching the end I found that my first solution was timed incorrectly and all the Lemmings got cut up by the spinning spike-log.
There are lots of levels later in the game that require proper timing like this. At least one level has some boxed-in weasels with switches that, as they walk left and right, enable and disable platforms. This requires the player to get the timing right in order for a Lemming to pass the platform without falling to its death, eventually to do away with the pesky weasel.
I've always considered Lemmings something that you could theoretically plan out from start to finish just by pausing the game at the beginning, but when things change depending on what time it is, it, for me, just throws in an element of irritation that I don't care for. So my question to you guys: is the idea of "proper timing" a reasonable consideration in the creation of Lemmings levels?