Hey Pat: My responses are:
1. Does anyone have experience with the shelf life on immersion white tin? If so, how long can the boards be stored without adversely affecting solderability. I've heard one year.
No, we don�t, because we turn boards faster than that. We�ve heard the same nice story. So, why do you want to store boards for a long time, anyhoo?
2. Does anyone have experience wave soldering white tin? If so, is the grainy appearance of the solder joints indicative of possible joint strength problems?
Yes. Alone the grainy appearance doesn�t mean much, although it (1) is not indicative of white tin and (2) is indicative of the approach you take to wave soldering. We wave solder shiny solder connections with white tin. Although, we could make the connections grainy, if we wanted to do that (which sometimes we do whether we�re supposed to or not). Of all the ways to make grainy connections, the easiest ways I know are: (the good) get the connection blistering hot and cool it slowly, (the bad) move the connection while it�s cooling, and (the ugly) wait before washing an aqueous flux. Check the archives for more background on grainy solder.
3. Has anyone experienced large variations in solderability from batch to batch of new white tin boards?
No, but with immersion tin being an electroless process, fabs do not control plating thickness well (same reason you�d be complaining about OSP thickness control, if you had selected that). So, if your fab�s a maroon and can�t control their process you�ll get poor solderability of thinly coated boards, same as when they�d mess-up the thickness of HASL boards. What kind of incoming solderability testing are you doing on boards?
4. Does anyone using white tin require operators to wear gloves when handling these boards?
No, we run aqueous flux. Either way, it�s good when operators try to keep their mits off solderable surfaces of boards, regardless. So, what�s the intent of the gloves? Are you running no-clean? Tell me, if someone scratches their nose while wearing gloves, ...