Fixing the drains wont necessarily help, it depends on how much you wash your car

I know as i've had to fix mine twice, and last time I cleared the drains and sealed the Cr@p out of the motor housing. You're best relocating the motor in the boot.
Its an easy job, I did mine tonight and it took a very steady 2 hours.
Roof up
Take out the plastic housing at the top of boot/trunk - be careful not to damage the microswitch.
Take out about 4 of the nearside roof 'hoop' 10mm bolts and un-hook the nsf of the hoop from the metal hook/clip.
Roof 1/3 way down
Remove nearside Half of the Rubber strip
Remove the 2 interior inspection holes (parallelogram shaped vent and round gromet) - Remove 2 large torx bolts
Lift up the roof clear of the car - place the lowest point on a piece of wood or similar to protect the car and maintain the lift height.
You now have plenty of room to pop your arm in and pull the motor housing out. Just make sure that if you un-bolt the motor, make sure the motor is face up or you'll spill the hydraulic fluid.