I recently discovered a little useful trick for gold digging using a ninja refresh passive.
Here's the video:
After your ninja kills an enemy, immediately move other unused units in his aura area.
The moved units will get a chance to be refreshed after moving.
I haven't tried this trick in Assassin one yet (since I don't have one yet), but maybe it will also work.
Now you can save up the leaping skill for when the ladder is actually too far. :>