My last meltdown was 2 to 3 weeks ago.
The thing that usually triggers mine is the display by other people (usually NTs) of ignorance, apathy, selfishness and blindly patronizing cruelty. My frustration is currently building up and near the point where I need to let it out through a meltdown, but so far i have remained in control. This is not good though because it is all being internalized. Yesterday I went out for a walk and let out some of the frustration, but the cold attitude of a few people along the way made it a break even situation.