I think the the biggest consideration in maintaining your group's web site is participation. Does your group have enough people who have the skills and willingness to help maintain your group's web site for the long term?
I suggest that you model maintenance of your web site on how your organization handles printed matter. For example, if your organization's newsletter is produced by paid staff members, then consider allocating the resources for staff to maintain the web site as well. Getting the knowledge and skills necessary to maintain a web site shouldn't be much more difficult than the skills and knowledge for creating a newsletter
From what I've heard, many religious groups that have web sites rely heavily on one or two volunteers to maintain the site--usually the same person or people who proposed and created it. However, if your group has approached its web site as an organization up to this point, hopefully you've attracted several people to the project, and you've designed a site that your group can maintain easily with its given resources.
Assuming you have sufficient human resources, then the concern is coordination of efforts. If you have pages that need to be updated weekly, for instance, make sure that the person or people who are responsible for updating the pages get the necessary information in a timely fashion, just as your group would do with information for bulletins, newsletters, and other printed matter.
Another concern that I've seen in religious organizations is the perception that if you're not a computer savvy person, you can't help out on the web site. That concern must be overcome for the web site to be an organizational success. Find ways for people who don't necessarily have technical skills to participate.For example, if some of the people who want to be involved in your web site project have access to the web but don't have the technical skills to help update the pages, then assign them the task of checking the web site on a regular basis. They can proofread updates, check to make sure that links from your pages are still working, just make sure that your server is up and running correctly, etc. Get creative here.
You might also work out some means of making new versions of the web site available to select people before they are published. It can be very embarrassing to proof the "live" version of the web site. I often place new versions in a password-protected sub-directory on my web server. Then, when I ask people to give me feedback, I give them the location and the login information. You may even need to implement a low-tech method, such as copying all the site files to diskette and passing it to people to test from diskette before you publish it.
Next topic: What is a Web Site?