I've been using the 30 sec. on/3 min. off type timer for about a year now and, knock on wood, all is working well. I do keep the electronics covered - not waterproof but splashproof, and I think that makes the difference. Also, I'm using the full 12 volts, but I keep my inlet fitting (HomeDepot/Lowes variety) pointed downward, and that doesn't seem to overly stress the bait.
Some options - waterproof box from most Walmarts - the small size is enough room for the timer/switch electronics - about $5 and change. Additional flow restrictors for the inlet - put a series of small holes in a cap for the inlet or add additional holes to a garden bubbler... hope this is some help
John