Removal of unmaintained ports - when?

While getting more and more comfortable with my FreeBSD 10.3-RELEASE setup, I noticed that a lot of ports lack a maintainer. The per port notice pointing to informed me that 4585 ports lack a maintainer as of today's date. Hence, several questions:

1. How quickly will any/all of those ports be permanently removed from the Ports Collection?

2. Is it in general risky to be using an unmaintained port?

3. Would it be fine for at least theme or icon ports, which in theory are not compiled and merely contain image files?

I'm sorry if those questions have already been asked, though I could not find any information myself.

I would be more than happy to claim maintainership of some of those orphaned ports, though I also intend to contribute to the Documentation Project and my time is a rather scarce resource :(.
As long as they continue to build and work, ports without a maintainer are generally not removed. If they need modification to work, that is when removal is considered.

So lack of a maintainer is not a huge concern, but if you can pitch in to maintain any of them, it helps everyone.
Even if they are removed the ports can be resurrected at later time, the SVN repository has the full history of every commit that was done to the ports including the deletion.