hate to be pedantic, but lead DOES corrode. wont have any bearing on whether you can wash pcbs or not...
If I recall, Lead is rather stable. After my father's death, I discovered some lead bars that were exposed to the elements for at least twenty years (likely far longer). Lead bullets from the Civil War are still found found on battle fields.
It takes some pretty specific circumstances to cause lead to corrode to where it might cause any concern.
like i say, i was being pedantic. do this. take a lead sinker, tyre weight etc. what colour is it? scrape the surface with a knife. what colour is it now? how long before it's the old colour again? that is corrosion, and pretty fast too. although it doesnt seem to go any further once its tarnished. sort of self-sealing i suppose. none the less, lead corrodes...
My point is, your statement:
hate to be pedantic, but lead DOES corrode. wont have any bearing on whether you can wash pcbs or not...
makes it seem like that a person should be concerned about corrosion of the lead on their PCB's. Yeah, I know you did qualify your statement by saying that it won't have any bearing on whether you can wash your PCBs, but seems to leave the reader wondering what environment would destroy their lead based components when in fact that kind of concern would be too far down the list of things to worry about. Probably right below worrying when your plastic and ceramic components would start to crumble due to age.

IIRC from rather sucky highschool science courses, the very thin film of lead corrosion is chemically bonded with the lead below preventing further corrosion from occurring. This has made lead exceptionally desirable for some really nasty applications, like lining toxic waste tanks. I never actually thought of it as "self sealing" though. I guess that's a kind of modern way of looking at it.