[OSM-newbies] Updating info for an old Tiger road

[Doug Hembry]

I'm sure this must be good answers to these questions, since old Tiger 
data has been fixed up by community members for years - but I'm a 
newbie, and I can't find clear answers in the wiki, or in the forum.

Q1: "Old" Tiger imported roads have various Tiger tags: tiger:cfcc, 
tiger:name_base, tiger:county, tiger:source, tiger:tlid, etc, as well as 
tiger:reviewed=no. Once the road has been reviewed and adjusted 
(carefully - how is not the issue here), which of these tags can be 
removed as no longer needed? I assume tiger:reviewed=no can be deleted, 
but what about the others? Should a new source= tag be added to reflect 
the review, alongside the tiger:source= tag?

Q2: A special case of Q1: Some old roads in this part of the US 
(California, SF Bay Area) have been absorbed into "Open Space" lands (a 
sort of Bay Area green belt). The map still has old Tiger data giving 
them a name, all the tags mentioned in Q1, and often designating them as 
highway=residential. But on the ground today, the roads have 
deteriorated into tracks, maintained as fire roads and for recreation. 
The road name has fallen out of use (no road signs, and trail names 
often different from their old road names). How to handle this? Do all 
the old Tiger tags go? Does the name= tag go? It seems a pity to discard 
the old information about what these tracks/roads once were - they are 
pertinent to understanding the historical record of the region, even if 
the renderers don't use such information. Is there some way to modify 
the old tags as no longer current, but leave them in place?

Q3: A special case of Q2: In some cases, these old Tiger roads have 
disappeared completely - overgrown and no longer in use, leaving perhaps 
only the outline of a road bed  and an absence of large trees. Should 
all the information about such roads be deleted from OSM? Same concern 
applies as for Q2.

What's the consensus on best practices for such situations?
Thanks!