I've found that any kind of tennon on a router table is very dependant on the thickness of the stock and how straight it is. This applies not only to small tennons such as in a face frame but even more to tennons in carcase constructions that may be as long as a shelf is wide.
For this I use a Woodrat instead of the table. The tennons are dead accurate and repeatable. Haunches are very easy to add (or leave wood behind for <grin>) and though I usually stick to about 1 inch long, 2 inches are an easy possibility. In the long shelf-end tennons, slight curvature to the board does not affect producing a straight tennon and not affected by board thickness.
...Doug
For this I use a Woodrat instead of the table. The tennons are dead accurate and repeatable. Haunches are very easy to add (or leave wood behind for <grin>) and though I usually stick to about 1 inch long, 2 inches are an easy possibility. In the long shelf-end tennons, slight curvature to the board does not affect producing a straight tennon and not affected by board thickness.
...Doug
