I have a full Bowman, Topps and Fleer run. For Topps I generally will buy recurring print defects as well as true variations through 1994. After 1994 and for all my Bowman and Fleer sets I have only collected variations listed by SCD, Beckett or in the PSA master lists. Have to have some limits
1991 Topps is the absolute worst. I do not think a master checklist is even feasible