Nevertheless , My Three Sons ended its primetime run in the spring of 1972 after 12 years on the air .
To save the series , CBS moved it in midseason back to Thursday nights at 8 : 30 pm , its old time slot .
My Three Sons ended CBS 's primetime run in the spring of 1972 after 12 years on the air .
To save the series , CBS moved it in midseason back to Thursday nights at 8 : 30 pm , its old time slot .