The hinges are very durable. they're made of thicker metal then stock hinges. But everything is only as good as it's weakest part. I have had Lambo doors on my xB for a few years now. it's a daily driver and I open my doors up as much as possible. this puts a lot of wear and tear on the hinge and the bolts etc. I did brake a bolt once. I was able to replace it myself. The process does involve usually taking the fender off to get to the hinge itself. Other than that I haven't had any braking of the product itself.
Now with that said it stays open via a gas shock. The gas shock is basically a bigger version of the one you can find on the trunk or hatch of most vehicles. these gas shocks do not like the cold. therefore opening the doors to the up position in winter is probably not going to happen. well that is if the temp is below freezing.
Also the bolt I mentioned before broke while the door was in the up position. not good if you're getting out of the vehicle or something. Even with the bolt broken you can still open and close the door. although I did have to lift up a little bit.
With that said you can still open the door regularly to an extent. I would say 45 degrees depending on the vehicle. if you're a bigger person this may not be the best idea.
the things you have to worry about are the reliability of the gas shock and the bolts.
I love these doors and to be honest I would like to put them on any vehicle I purchase from here on out. They're different, they're fun, they catch peoples eye. are they practical? well that depends on you and the car it's going on. if professionally installed you shouldn't have to worry about them for atleast a few years. and even then it'll be something minor.
You also have to learn that when ever you're expecting passengers you have to for warn them about the door. if they go to fling it open like a normal door it could hurt the fender, the hinge, and even the person because it'll bounce back and hit them. lol... Seen it happen. you usually have to give lessons on how to open and close the doors properly. Or any time you go to get it serviced you also have to warn about the doors.
Over all I would say they're reliable and fun but they have their disadvantages as well.