Finally today, after six years I managed to play this game through. All plots expanded, close to 100.000 energies in the bank and so forth.
However and what came as a surprise when expanding to the max, you will lose the possibility to collect trade tickets +99, and you cannot trade them for expansion permits and explorer permits. That would have been probably the last reason to hang out here anymore.
Why cannot you continue collecting and trading those for future purposes?