consecutive travel plans

Yes you can.  Just make sure the travel pass is removed from your add-ons, then you can text and add the new travel pass.

Note that travel passes are are for postpaid account only.

Will the 30 day travel pass automatically drop off at the 30 days or do I have to remove it myself?  If I have to remove, how do I do that?

It should auto drop off, but I would double check just in case as there have been issues in the past

Who do I double check with?

You can check in add-ons in self-serve if it dropped off or not. 

If it hasn't dropped off, how do I delete it?

In your self serve account under Plans and Add-ons, click Manager Add-ons, then you just click the X next the the 30 Day Europe Travel Pass.