I'll quickly summarize what I've read on this thread. First, my background is 15+ years in product management for Personal Lines insurance, including 3 years of running the pricing area of Motorcycle insurance for a very well known insurer.
In general, most of the sentiments here are correct. Insurance companies do typically slowly raise rates (1-3% per year) on long term customers. The theory being that these are small enough that the insurer won't switch, and are needed for inflation and loss trends. To offset this, there are loyalty rewards, etc.. That is without there being a general rate increase across the entire book of business for the state.
I am also a shopper, but stick to well known companies. You can get quotes from 3-5 large companies in well under 1/2 hour. There are enough large companies that by cycling through them (Geico, Progressive, Allstate, State Farm, Liberty Mutual, Farmers, Nationwide, Hartford, Travelers, to name a few) you should find a good price. For MC specifically, add on Dairyland, Merkel, and apparently Haggarty.
Lastly, your liability limits are your choice. but I've seen multiple MC claims payout hit their limits and then our insured by sued for more money. One at fault accident resulting in grievous injury or death of the other person is not only tragic, but could ruin you financially. Just my two cents.