Yep I get them for around 5-7 days most cycles. All others signs confirm O for me two days after my first + opk. (CM..temps...cervix position)
I like the Answer brand too but they are pretty sensitive. I have had good luck with the internet cheapies too, but usually only see 1 +. I would rather see them for 5-7 days instead of worry I missed my surge. That's just me though. At first all those +'s drove me banannas!
Good luck hon! Now go get those sperm.