Before you shop around, I recommend that you email your SF agent. Here is the email: "Dear SF Agent, I have been a customer for many years. My total annual premiums are XXX. Over the years, the premiums have increased at a rate higher than I feel is reasonable. I have had no claims, have all my coverage with you and have maintained a great credit score. I believe that the reason for coverage is to prevent a catastrophic financial situation in the case of a claim, not to reimburse me for small dings and cracks. I would like you to look at my policies with the eye towards jacking those deductibles through the roof, increasing umbrella coverage and eliminating unnecessary coverages. Since my car is old and has little value, I want to drop Comp and Collision. I want liability only."
Please note that I do not know your personal situation so I don't know if you have an old car.
You can see that I believe the purpose of coverage is for the big stuff such as a $500,000 claim, not multiple tiny claims. Underwriters do not like multiple tiny claims.
In my situation, I keep the UM/underinsured motorist as low as possible. My situation is different than BingyBear. I do not know yours.
Please note that this overall strategy does not work if yo want insurance to cover every little ding, scrape and storm damage.