I want to know if it is appropriate to join tables from different years to the same census tracts TIGER file.
If all census tracts' IDs do not stay the same, then how would they change when adding new tracts, modification, merging, etc?
The Short Answer: No. Census Tracts do change over time (Especially from 2000 to 2010 when in many cases they appear to be essentially redrawn).
You can use the faces files to compare the same geographic area with its 2000 Census and 2010 Census assignment using dissolve techniques. You can also check out the relfiles to compare 1990 Census with 2000 Census using aggregation techniques.