The steel ones should be ok for at least a season again if you dont have a massive accident that shears parts of your car. If you use solid on the front that puts strain on the shafts as well. after each race check the axles to see if there is slop in them. clean them and go race... you should be fine.
When I go racing I have 2 sets of spares just in case and if I see any slop wear or tear I replace both left and right with the new ones and rebuild the old one when the day is over.
Again for wide open tracks I use the light weight axles on front and rear. for tight tracks steel fronts light rears and If I go local racing at tight track I use steels all around.