Stock O2 sensors are always in a compromised location thanks to emissions standards. They are usually placed close to the exhaust ports (it must be in a non-pressurized location though, which is why they aren't pre-turbo) so they will heat up and provide a reading more quickly so the car can enter closed loop mode and control emissions more quickly after start-up.
A wideband will work in a hot location in a pinch, but it will sacrifice some accuracy and life. The stock O2 sensor on my Mazda is a wideband and it's right on the turbo outlet. It's hot as hell right there. The sensor actually has a 3" round cone shaped heat shield that's attached to the sensor to protect it a little bit. The reason Mazda put it there was because they needed to measure the AFR before the primary cat, and the primary cat had to be as close to the combustion chambers as possible to heat up and light off as fast as possible to meet emissions standards.
On the Mazda I just changed it at 110,000 miles because it died and stopped putting out a signal completely. It's the first wideband I've ever seen die. It was an NTK wideband sensor, not a bosch like most aftermarket wideband kits use.
I put the Bosch LSU sensor on my Supra down right in front of the cat, on the downpipe. Probably the best location on our cars, it's got ample airflow and the exhaust has cooled down quite a bit. Just be sure to locate it in the upper 90 degrees of the pipe to keep condensation droplets from ruining the sensor.
