There's Hope

Droughts and dry spells drain the life out of most things. Animals lack food, the trees loose their foliage and the grass becomes brown and it looses all its softness, but what happens when a Christian is going through a spiritual drought? We're told there's hope no matter how lifeless our spiritual life is and to "not give up", but how long do we have to wait before we finally get a 'spiritual downpour'? And is it too late for some?