We too have a My3.
I used some old mtb inner tube rubber as tyre liners and added Inner tube slime. No unwanted deflations so far <Fingers crossed> and they should hopefully re-inflate with the pump if it does happen.
The chassis is not strong -the base of the handle, especially when extended, is a a weak-point.
Despite having never taken it anywhere more gnarly than the Trafford Centre, your honour,(c.f. "I was just riding along"…) At 4 months we had our frame replaced (I kept the slightly modded wheels). The new one felt much more sturdy, so the original one's joints must have loosened over time.