I can guarantee you that this is every photographer’s worst nightmare, which is why any wedding photographer with any sense has their equipment serviced regularly. I use professional equipment, which is specifically designed to withstand the pressures of a professional wedding photography environment and I have it serviced twice per year, so that it’s always in tiptop shape and so that I can rest easily.
I also ALWAYS bring spares. And I mean spares of everything. I never leave the house without a spare camera, lots of lenses, lots of memory cards, spare batteries, spare light stands, spare flashguns… you name it.
Oh yeah! I take this stuff reaaaaally seriously!