Hi Slucky,
I also replaced the HID bulbs on my "new-to-me" 2006 IS250 with Osram D4S items a few months ago and so far they seem to have solved the problem of the lights turning off intermitantly. When researching the problem I came across multiple warnings about the number of counterfit Philips and Osram HID bulbs on the market which apparently are prone to early failure. I mention this just in case you cannot vouch 100% for the seller from whom you sourced the bulbs - you do not want to go to the trouble of replacing the ballast only to discover that the problem was your "new" bulb!!
Dec.