Never ever make the mistake of using silicone grease inside a cv joint.
Use the correct cvj grease and never overfill it. Always fill the required quantity of cv grease which is 90-100 grams in small to medium cars for the outer joints and about 150-180 grams in the inner tripod joint (which does not use cv grease)
Overfilling, not burping and wrong clamping of the boot causes rapid boot failure, you should also look for original thermoplastic cv boots rather than replacement rubber ones for outer joints, the thermoplastic ones have extremely heavy duty clamps which require a heavy tool to tighten so make sure your mechanic has it. Using cheap thin clamps on genuine thermoplastic boots is a waste of time and effort.