No longer open year around. Check the NF website for dates. Also trails will close after heavy rainfall.
First trip here in 1998 was great, although very dusty. Trails were still rugged and challenging. Except for trail 3 and 313, most of the trails have been worked into roads that are not fun to ride. Environmental nuts have nearly gotten this place shutdown. Many trails have closed since 1998 and the only trial currently open to get all the way across the system east to west is Trail 6. Trails that don't make a loop aren't that exciting to ride.
Go to Fourche Mountain if you want to see what Wolfpen was like 20 years ago. Wolfpen is mostly disappointing now.