I recently purchased some collapsible trekking poles (Komperdell Ridgehiker, made in Austria) and found them quite useful in terms of being able to extend or retract them slightly for going up and down hill when my knees are most strained with my 30-40 pound pack.
A major issue with the design was that it snapped at the plastic rings that make up the joints while going downhill with only a 15 pound pack and fast pace, with conscious effort to plunge them in a way where I would not bend them too much while moving forward.
If I am to be abusing the poles like this (absolutely am looking for them to be strong enough for the rare slip somewhere at a minimum) should I look for much pricier ones with stronger joints, or go with fixed? And if I choose fixed, should I size them at a 90° bend or should I size them for say uphill climbing or slightly longer for downhill and possibly adjust the hand loop much longer for when I use them for uphill? Or is the benefit of collapsing mainly for packed size and not much is gained by adjusting them for the incline?