I had excellent weather when I walked the TMB. There was an enormous thunderstorm one afternoon, and the campsite flooded, but didn't reach my tent. However, it was such a splendid storm that it was definitely a bonus on the trip.
When I walked the GR5, I walked the whole thing both ways, with all its variants and alternatives, and it took me a total of 10 weeks. Out of that time, 9 weeks saw perfect weather. There was only one really wet day, one day with blanket snowfall, and a few damp and misty days. Out of the entire trip, there was only one pass where I never saw the view, either on the outward or return trips.