Not necessarily - the policy (or policies) you create can be selected from the dropdown menu in the listing and then automatically applied (same with payment & return policies). You can create however many you need, but each different type of postage method and/or cost will become a separate policy.
eg sending a large letter with a registered option = one policy, sending a parcel with signature on delivery = a different policy. (i.e. each time there's a difference in services offered and/or prices charged, it needs a new policy).
If you mainly use the same postage costs for your listings, you can set one of your policies as the default and just change it if you need to.
Edit: Just re-read the question.... the answer to which is, yes.
