Since Jesus said we shall not know the hour or the day when He will come back, it makes sense that we probably won't know about when He will catch us up in the air with Him.  There is nothing that is air-tight on this issue.  So.... when it comes to what to teach, I look at it this way.

There are two possible times that most people subscribe to -- before the Great Tribulation and after the Great Tribulation.  There are two possible outcomes to our teaching -- we are either right or we are wrong.  So let's look at those four possibilities.

1.  If it happens after the tribulation and we were right, you have fortified the saints so they won't fall away during the persecution.

2.  If it happens before the tribulation and we were right, we have won more souls to the kingdom who wish to avoid the Great Tribulation.

3.  If it happens before the tribulation and we were wrong, we will be pleasantly surprised by what we have avoided.

4.  If it happens after the tribulation and we were wrong ...  we will have caused all sorts of Christians to have a faith crisis at the worst time in history.  Many will fall away, thinking they weren't saved after all.  Jesus said it would be better to have a mill stone tied to your neck and be thrown into the sea than to cause one of these Christians to stumble.

So, what is the safest thing to teach?