How long the plot will last is going to depend on how large a plot, your deer numbers and whether or not you can keep them out of the plot for the first 4-6 weeks. If you use something like the plot saver so the peas in particular can get some growth it should last all summer if the plot is a couple acres. Small plots don't stand much chance when it comes to summer plots...they eat em to the ground quick but if you can replant again, they are worth it.
Lablab is good but I think it is a little on the costly side. The iron clays and tyrone beans will climb just as well and produce the same type of forage and they are cheaper.
I planted the Athens mix last year in May and it made it thru the drought and the deer hammered the sorghum in early Oct. and stayed out in it until mid Nov (I left standing and mowed strips). It will def. be planted again. I also found the deer on my place loved the iron clay/sunflower plots I planted. If the deer ate them down I just replanted.