It seems that the places we miss the most are those, that were visited as tourists, most likely with close to their hearts people (or visiting those people there).
The problem arises when one realises that there are more of those places than actually free time.
We work usually 35-40 standard hours a week. Get 5-6 weeks of holidays a year (if u get more, lucky you!).
This gives a maximum of 5-4 weekly trips a year one can do to come back to the missed places.
i count a week for Xmas around family... if one is lucky :)