No, it's better to have at least a couple of addresses.
one personal address that you only give the address to trusted friends, family etc, do not ever post this address on a website, or use it for signing up for anything and it should not receive hardly any spam
then have another 1 or 2 disposable addresses that you can use for signing up to website, or for posting publicly, these addresses probably will start to attract spam, but when it gets too much just dump the address and setup a new one.
You can have as many different email addresses with most free providers (such a gmail) as you can be bothered to setup, and yes you have to go through the full sign up procedure for each address.
Lastly, it really makes no difference if all your addresses are with one provider or with different ones, the only exception to this is some providers (such as hotmail) let you link several addresses which can make it easier to keep track of them.