I'm putting up a lot of fencing so cost is a factor. Cedar is out. The lowest price I found for basic 6x8 cedar stockade was $85 a panel. So it's either pressure treated or stained. I found a nice looking SPF fence that is prestained wth water repellent stain but not pressure treated. If recoated every few years will this last as long as pressure treated?? If I get 8-10 years out of it I'll be happy.
Quality pressure-treated lumber, such as from Weyerhaeuser, Georgia-Pacific, etc., has a 50-year limited warranty.
Untreated lumber won't last but 1-5 years unless you keep it sealed or painted at least every other year.
Go with pressure-treated (usually costs about 30% more than untreated and more than worth it) or you'll be fighting to preserve your fence forever. Also, have yu considered and priced vinyl fencing? I don't know what the price comparison is to p-t.