I've got two sites around that age.
1) About 7 years old. Content has been pretty static over the years. Two major overhauls in UI. Traffic has been consistently 40k visitors a month for last 4 years. Up about 20% this year. No UGC.
2) About 13 years old. 3-4 major overhauls. Little UGC. We slowly add new content to the site. Less frequently update old content. Seen year over year growth consistently. Traffic has been > 1m visits/mo for years.