During a little winter maitenance I thought I would pull out the DDM 35watt bulbs that have been installed for about a year and 22,000 km and have a look. Both were still working.
There seemed to be some kind of transfer from the ceramic rod to the bulb glass itself (white spot in the middle). Not sure how good this is for bulb life, and especially any chance of them breaking and contaminating the headlight housing. I changed them out for the Morimoto XB35 watt 6000K bulbs and ballasts.
The XB35 and the DDM. You can also just see some warping of the bulb base on the DDM
I have the DDM ballasts and igniters mounted on the left and right sides, just back of the headlight housing on a couple of alluminum plates that fit in and the setup clears the forks fine with about 1/2 inch of clearence . The Morimoto have the igniters as part of the ballast and are a little more compact, but about 1/4 inch thicker than the DDMs. The Morimotos went back in the same location without any problem.
Crappy bench test pic. of the DDM 35 watt 4500K on the left (at least thats what I ordered. No identification on the bulbs or box) and the Morimoto XB35 watt 6000K.
Piece of cardboard between them and shinning on a white cloth.
Also had a good look inside the headlight housing after the year of operation and I don't see any damage or contamination of the reflectors which is why I wanted to have a look in the first place.