Guys you discuss something that is not worth that much discussion
1. There are no temporarily bought links to the site.
2. I don't have any other even more or less serious adult sites, neither I asked any of my friends to place links to it.
3. Some long time ago (5-7 years) I had experimented with link exchanges placing some recip links on my niche pages. Today I've checked this backend and more than half of those 20 links from other sites are down anyway
What really supports the site's positions are: DMOZ, thousands of niche-specific recips from submitted galleries and probably some natural backlinks.
Regarding stability - I can provide you with ATX stats which show that SE traffic is that much stable for more than a year, and there were absolutely no actions for 3+ years from my side to support that.