I found they work sometimes. I played a game of Altar in .80 or .75 and could build higher level Henchmen that leveled faster with these traits for sure. The started at level higher with Veteran and got more XP then other Henchmen. But on a second game at least Veteran didn't seem to work. I started a new game and tried Veteran again and it worked. I have no clue why.

Certainly in the unit design screen, if you select "Veteran" the unit's stats do not change (e.g. no increase in hp). I think that is a bug; it's confusing at least.

Derek:  thanks for your reply!  The Veteran and Experienced traits work fine before you save and exit.  But once you save and exit (even once), the traits never work again, ever, for the current game.   There is nothing hit and miss about it.  This bug is 100% reproducible.  I will try to post screen shots and saved game further down this thread (first time trying this for me).

Note that it is entirely possible to have one unit with a functional Veteran trait (created before saving and exiting for the first time) and another unit with a failed Veteran (or Experienced) trait from later in the game (created after saving and exiting for the first time).

Hope these can be fixed, or if not removed from the palette of traits. 

Custom unit design is one of the great features of this superb strategy game.  FE and LH are classics for sure and take up most of my gaming time these days.  Well done.

The sign of a good manager!

The real question here is why are you building Veteran/Experienced units?

Such a UP Trait. A level is pretty negligible bonus and the trait slot is better better spent on almost anything else. Add in slower leveling from that point on and it gets even worse. Very few races get any kind of real bonus from leveling.

Maybe make it +2 Levels?

Completely disagree.  The hp bonus alone is worth the extra production, especially at higher world difficulty levels where mobs start at a higher level.

spell resistance and spell mastery also increase. dodge only increases per level if you train units with the "acrobat" trait. the other stats aren't affected by level ups afaik.