While using miles for round trip flights sounds like a great way to spend them, for grand vacations don’t underestimate “Round The World” award tickets. For example, 125K All Nippon Airways miles (not that easy to earn) for business ticket is less than a regular round trip ticket on many airlines (see all business class award rates and respective miles transfer programs here). There are quite a few airlines offering dream itineraries, though you may have to be flexible with dates, and creative with options. Here is the list of RTW airline programs I know of. If you know any other program, please let me know, I’ll add it.