Do you find that it's the returning members who matter most to your forum? Yes, it's nice to get new members, but you want them to return, right?
What is unique about your site that gets members to return to yours over other forums? Is it that they have friends there? They trust the staff? They like the topics? Or they don't realize there are other similar forums out there? or what?
On an old forum I used to run, I think we got so caught up in trying to get new members to join that we started to neglect those who stuck around. We made many changes trying to encourage registration without consulting the active member base how they might feel about it. Some didn't go over well, and little by little there was less activity on the site. Which in turn leads to a forum that doesn't seem active and worth signing up for.
I think what made our forum worth returning to was the community we had and how easy it was to get into engaging conversations. It's definitely worth trying to build something great with the members who chose to spend time with the forum.
Getting users to return to your forum always helps it feel like more of a success! I have a resource board where a lot of people log in, find the code/skin they want to use that is hidden from guests, and never return. It's somewhat maddening, but I have a handful of users who log in every once in a while to discuss things or keep using the resources I publish. Having a Discord server seems to help bring some members back to the forum since I post every new resource that is released on my board in a channel.
In every business, it is best to retain your clients that to source for new ones. So it is the well established members that jeep the forum going, not necessarily the newbies.
I think having returning members looks good on your community. This could help bring in more potential members, if they see there's people sticking around then they might be interested in your community.
Returning members are important but you also need new sign ups. I value both. I try to make my returning members active as well as encourage new members to become more active. I believe the value your forum provides determines whether your users will be active or not.
