Once installed which shifter cable needs the least upkeep...prestretched or the regular stainless?

As far as I know they are all pre-stretched. The cheap bulk stuff we get from Quality is... and its all die extruded, blah blah. Cable is cable as far as I'm concerned.

HI
Makes no difference. After you install any new wire, swing on it awhile. Grab hold of ot along the top-tube and pull. Give it a good pulling and pre-stretch it yourself. It will make no difference to it's life but if its a gear wire, stretching it will stop your gears going out of index.

Most of the need for adjustemnt comes from the housing compressing and seating in the housing ends rather than the cable stretching anyway.

Pre-stretch is another marketing gimmick, so save your money. Go hang an old cable from a rafter and pull on it. See if there is any stretch. Then check the amount of tension required to pull a derailluer or brake mechanism. That's not going to affect the cable at all.

Otherwise, as Rev.Chuck says...

Uhh, as a science bloke with some engineering skills I would think that the change in temperature would affect the length of the cable as much as a pre-stretch. So in other words, I wouldn't stand there stretching the cables unless I am only riding the bike when it is exact 21 degrees celsius. :)

if I just replace the cable I see a little bit of adjusting needed after a week or so. thats without removign the housing. so next time I replace the cables I will try the ones I pre stretched. I hung 20# of weight on each cable and let it hang for a week or so. then I can compare them.