If you're "running up against a wall" after 50 targets, it sounds like you need to shoot 200 to 300 targets per day in practice several times before a big shoot to overcome your tiredeness or fatigue to compete effectively. If it's more "recreational" in nature, then there's no need to be concerned.
I know some of the top shooters will practice 2 to 4 days a week, for two weeks or more,shooting 300 to 500 targets before a big shoot.
If you get in a regimen shooting say 200 targets every time out, 100 won't seem as big a hill to climb as it is now.
Holding up the concentration for 10 targets at 10 stations is a little more daunting to me than shooting a round of 50 made up of 4's and 6's. Ever notice how many of your misses
come in the last 4 shots at a station when you're shooting rounds of 100 ? Looking back at a packet of score cards from a couple of shoots, I notice that 8 out of 10, 7 out of 10 and 8 out of 10 of the top 10 shooters at 3 different shoots ... had most of their "0"s" in the first 5 stations. They actually shot the last 5 stations at a higher percentage !