Some insurance companies will offer you deals if they are your sole insurance company. However, those discounts might not compensate for the lower prices of going through a couple companies for each insurance need. It's just a matter of who you trust and feel comfortable going through. Also, having various insurance companies can be helpful if one company gets bankrupt or is bought out by another company that might increase your rates. It can be a safe guard in that sense.

I think the cost of a policy really depends on a lot of things. What type of policy is it, where do you live, are health conditions a factor... see where I am going with this.. Just because you have your home insurance with one company doesn't mean you should obtain a life or health with the same company.