Life insurance companies consider your income, assets and liabilities, among other things, to determine the maximum amount of life insurance you can own overall, including all policies you have.
They don't want you to be overinsured, because life insurance policies do payout a death benefit for suicide if the insured person takes his/her life more than 2 years after starting the life insurance policy (one year on some states).
As for how many life insurance policies you may own - that's up to you.
You can have several life insurance plans, but the insurer is most concerned with the total amount of life insurance coverage you own over all of your plans.
You can use a life insurance need calculator to help you decide how much life insurance protection you need.