Sirius XM Radio (SIRI 0.96%) is back to hitting multiyear highs again.

The satellite radio provider hit $3.25 yesterday -- and again today -- revisiting its four-year high set earlier this month. You have to go all the way back to late March of 2008 to find the last time that Sirius XM traded higher, and that means if Sirius XM can stay around these levels in a couple of weeks, we'll be eyeing this as a five-year high.

Why stop there?

The one thing that we can say is that Sirius XM has never been more valuable. Sirius was still a stand-alone company at this point five years ago. Regulators would finally clear the merger between Sirius and XM later that summer. However, even on a pro forma basis -- combining Sirius and XM before the deal was complete -- Sirius XM has still never been this valuable.

Liberty Media (FWONA) acquired a 40% preferred share stake -- boosting the effective share count by 67% -- in 2009. Before that there was a huge recapitalization, and Sirius XM has been naturally loose with offering stock options that pad the share count over the years.

This is important, especially as bears and even some nostalgic bulls pull up stock charts and historical price tablets showing Sirius at loftier levels in the past. If you ever wanted to buy Sirius XM whole, it would cost you more now than ever.

Why not?

Sirius XM itself has never been more popular. It closed out its latest quarter with record revenue and subscriber count levels. After years of being tagged as transitory technology, Sirius XM has proven its viability as a premium radio platform. A few base and secondary rate increases along the way have also validated Sirius XM's pricing elasticity.

The skeptics are certainly out there. A whopping 406.3 million shares were sold short as of the exchange's latest mid-February snapshot. It's the most bearish wagers placed against Sirius XM over the past year.

However, Sirius XM has earned the right to be at its most valuable point today. There will be challenges in the future, but Sirius XM has climbed larger walls of worry before.