How to keep that bright, new sting zing?

You could try the technique of soaking the strings in denatured alcohol. Which can bring some life back to the strings. The following link should help: http://www.tunemybass.com/strings/how_to_clean_bass_strings.html

Using the cleaning method above will only help to a point. Ultimately if you love the sound of fresh strings. The easiest thing is once the tone gets "dull" just replace them with a fresh set. No amount of cleaning will fully bring the tone back 100% long term in my experience. All strings lose their "zing" after a while. I'm not sure experimenting with different sets would help too much. I suppose it depends how you define "zing". As certain strings sound brighter then others when new.

 

One simple thing you can do to extend string life is to wash your hands before playing, and then wiping the strings down (both on top and underneath the strings) when playing.

 

Treble knob on your amp. I HATE new strings.

 

I had a set of the elixer strings and they stayed bright for about 6 months. They cost more, but I think it's worth it.

 

As in bright as the day you got them for 6 months? Even with slap?

 

Dean Markley blue steels. New you'll prob be dialing the tone or treble knob down a good bit till theyre well broken in. Once broken in they sound more like regular new strings for long time. Brightest stainless strings I know of. Great crack of thunder bass too. But overly trebly at first till broken in well to me.