Privacy: Do you know of a no-registration email forwarder that lasts longer than 1 month?

Use Thunderbird as your E-mail application. Create an "identity", which is merely an alternative E-mail address. This is a handy capability of Thunderbird. You can not only send E-mail from the alternative address, but you can also receive E-mail at that address.

Yes, you do have to register the alternative address with your ISP. Later, you can delete the identity and unregister its address at your ISP.

I use gmail for that purpose.

I got a free domain name with DYN, and later switched a different one with NO-IP. I use ddclient, to keep the record pointed at my dynamic IP address.

I run an exim config that drops all mail for my domain in a directory where I can check it as needed.

this does nothing to hide my ip address though, so doesn't offer any sort of real anonymity. but I've stopped worring about signups spamming my in-box.

Are you wanting this just to avoid (or rather reduce) spam, or to conceal your identity for other reasons?

Some ISPs put a limit on the number, and/or charge, for that, though.

Some ISPs - and most hosting/forwarding services - allow you to use anything before the @ sign, without having to register it; I use that for anything that requires an email for registration etcetera. I usually use the name of the company/site involved, so I know who leaked it if I do get spam. I don't get _that_ much spam, so I have my email software set to collect emails with anything before the @ sign, as it's easier and I don't have to keep changing its settings; but you could set it to only accept certain ones, you'd just have to add the new one and then remove it after a while. I imagine that represents about the same amount of effort as setting up the forwarders you are seeking.

Obviously, this only works where you own (or rent) the bit after the @ sign; no use to anyone whose email is just something @bigISP.com. I see the OP's email ends "@ziggo.net" - do you own that domain, or is it your ISP?