There's always a chance you'll not be able to ward again especially when it expires and your lane is pushed beyond the river, and by the time you head back to throw another ward the enemy jungler may already be waiting there D:
I totally agree, its a frigg'n death trap to ward at hard times in a game. lol I try to tell my ad carry to get fed close to the turrets safety so that ganks will be difficult. Also in hope that our jungle will take advantage of an over extended enemy by chance. But it only helps so much if enemy bot or jungle is not fed.