The most recent Windows 10 Mobile Insider Preview is currently build 10512, which was released to the Fast ring just over two weeks ago. Before that, a full month had passed following the rollout of build 10166 in early July. The first Mobile preview came much later than the first PC version, and new Mobile builds have been less frequent too, relative to the PC releases.
Faced with this information, one question immediately springs to mind: Why?
Today, Microsoft's Gabe Aul offered a bit of insight into the situation, when he responded to an enquiry on Twitter on the subject:
Aul pointed out that Windows 10 Mobile lacks the 'patching' capabilities that are present in Windows 10 SKUs for PCs. As he says, when a bug is discovered on Windows 10 for PCs, it "can be patched without [a] new build." But when a bug is found in the Mobile SKU of the OS, it's not just a case of applying a quick-fix with a simple patch.
Instead, as Aul says, they need to 're-spin' - in other words, a new build needs to be compiled and tested internally, before it's finally assessed as a possible candidate for release to the Insider Program. This, inevitably, takes a lot more time than hot-fixing bugs with a quick patch, and accounts for some of the extended periods that pass between the release of new Mobile builds.
Of course, none of this brings much comfort to those eagerly awaiting the next preview - and Aul had some bad news on that front today as well. He said that 10530 was a candidate for release, but "one key fix" hasn't yet been completed, and as a result, a new build is "unlikely" to arrive until next week.