Agree with all of the that. His age is a tiny fraction of the ridiculousness, enough that it's not even worth mentioning. The real reason you don't see a ton of 42 yr old pros is that guys just get tired of it. Horner strikes me as a guy who will never stop racing, ever. He loves racing more than anyone I've ever seen. I bet he'll go from a 48 year euro pro to a 49 year old going back to try and win Redlands, then maybe racing cross full-time.
While there's a slight loss in vo2 as one ages, the effects are small. Also the studies available tend to look at untrained subjects, not guys who are still active. Whatever detrimental effects his age has on his performance, it's more than offset by the fact that he's carried an awfully light race schedule over the last couple of years. Even with all of the top guys juiced, guys still get tired. Whether real or contrived, he has a lot of "knee injuries" that keep him from racing a lot. That's a pretty big advantage he has going for him, that would more than offset a 1% loss in vo2.
I seriously doubt there's any new and improved doping going on. I agree with Rasmussen: he's not doping, well, anymore than he used to...
As far as this being 'sudden form', I have to say that his comments on the subject reflect my own thoughts. He's had this ridiculous form plenty of times. Thing is, he's a stage racer who's not a great TT'r, so that doesn't give him a lot of options. He also can't sprint, so that's going to limit his options for big wins, unlike a guy like Dan Martin or Hesjedal--guys who can climb but have some pop. Lastly, he's always been a legit "team player". Again, unlike someone like Hesjedal who rode at 90% in the team role, hoping for his chance, Horner always sold out in that role (Lotto, RS). Really not the best thing for career advancement or to get results.
In other words, his ridiculous form is no more ridiculous than it's been in the past, IMO. And it's no more ridiculous than the form of Nibali or Valverde, et al.