I have used Fuji f31fd housing for 3 years and have never used its silicone gel.  I don't apply silicone gel at all.

I have used Fuji f31fd housing for 3 years and have never used its silicone gel.  I don't apply silicone gel at all.                                                                                                                                                                                                                                                                                                                       

I have dived and used housing for 8 years.  I have never applied silicone gel.  I did the same thing for my old Olympus housing.

I think silicone gel helps to soften the o-ring so it is not easily dry off.  But the weather in HK is not too dry.