Manamune is bad for jungle, maybe increase to 4 charges every 16 seconds?

If manamune could collect 4 charges every 16 seconds this would be very helpful for junglers. It's not a very popular item and it wouldn't change it that much, it would just help the jungler's if it was changed to (can collect 4 charges every 16 seconds) who have to roam a lot between camps and this would give them the ability to max it in a period that is faster than 45-50 minutes...

also; bug?: manamune did not look like it was collecting charges from kassadin's teleport ability