I've have a wonderful trek Annapurna base camp is so worth the hard walking to get there! Everybody can do it if they want to Rishi was the perfect guide too, very great English and really a lot of helpful. I recommend his company Encountersnepal.
AMS Reserch Trekking in Nepal
In 2003 Rishi was the guide for a research trip to lobuje (5000m).I did my PHD on sleep and breathing at high altitude studying 20 people over 3 trek in the khumbu