I'm not the one to help you re far flung places anymore. Been there done that and am finished with long flights now, and I'm older too!
However.... if it's Europe and you feel like moving around a bit there are three trips that I did in the past couple of years and all were great. Might be of interest to you. 8 or so days each, but you can stretch it out a bit!
Fly into Seville, train to Cordoba, then to Granada, then to Malaga city, fly home from there. Trains are so easy and cheap in Spain, and each of those places is incredible. Andalucia is just magic. Did that end of Feb, and while it was warm and dry it was not hot hot. Great for walking and being active. Hard to move around in intense heat.
Fly into Marseilles. Hire a car, go to Avignon, Arles, Aix en Provence, Nimes and Montpelier. Fly home from Montpelier. Absolutely amazing, but more expensive than Spain.
Fly into Treviso, train to Padua and based there, local train to Venice for the day (30 minutes). Train to Ravenna, then to Bologna, another day in Venice, day trip to Verona. Busy schedule but worth every minute.
I'm 67 now and planning the next one which will be Belgium and Netherlands. Later in the year for a bit of warmth.
Enjoy your trip. I think you will head off long haul though, and why not. Let us know where you decide. I enjoy reading about the travels of others!