Microsoft watcher Paul Thurrott writes: After I asked about whether the free upgrade for Windows 10 Mobile would end on July 29 as it is for Windows 10 for PCs, Microsoft's Dona Sarkar clarified the firm's evolving strategy: The Windows 10 Mobile upgrade will now continue to be free past the end of the month. "So, the free upgrade to Windows 10 ends for Windows phones on July 29, too. Right?" I tweeted yesterday morning, seeking clarification for a reader who had asked me this question. After all, Microsoft had said nothing about the expiration of the free Mobile upgrade since last year. "Clarification from this morning," Ms. Sakar tweeted later in the day. "The free upgrade offer for PC ends on July 29 but as always there are no implications or cost on phone." Hm. Not sure about the "as always" bit, as Microsoft's plans for the free Windows 10 Mobile upgrade have changed repeatedly since the firm announced this upgrade in January 2015. And over time, many of these changes enraged users who had believed earlier promises. You may recall that the original plan was to upgrade all Windows Phone 8.1 handsets to Windows 10 Mobile ... for the first year only. But over time, that changed. It was going to be all handsets with at least 1 GB of RAM. And then it was going to be some subset of handsets sold over the previous two years, but not the Lumia Icon for some reason.