Great question but there's no answer. This is ultimately up to the consumer - you need to know what can happen and how much it can cost, and work with your agent for pricing of various limits and deductibles, forms and insurance companies. Then, you decide - and you'd be surprised at how little a higher limit can cost.
Most claims are smaller, so higher limits don't cost as much as the basic limit might. I always recommend as much coverage as you can comfortably afford and which suits your particular situation.
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