When you wrote "Yes we first cleaned up the ball bearings in the switches but it didn't last long and so bought new switches that failed quickly." -- You did not mention the contacts -- were those cleaned? As others have suggested -- too much voltage? -- too much resistance in the window regulators? -- due to lack of lubrication - or misalignment of the regulators (the screws/nuts that secure the regulators can loosen and allow the works to shift and bind). -- Dave