We are testing our website navigation and content arrangement before we begin the redesign on our informational website. We want to know if users can easily find what they are looking for and see which content needs to be easier to find. We are going to ask volunteers to find content that we think most users will be looking for on our website (based on web analytics and the purpose of our site).
We conducted practice user tests and there were a couple of things that users just could not find. After looking for a few minutes some testers gave up and some just kept on looking and got frustrated. Our practice testers found most of the things we asked them to find in 30-90 seconds. Some testers spent over four minutes looking for one question before I asked them to move on to the next. Is it okay to mark a question as a fail and move on to the next after a set amount of time has passed (e.g. three minutes)?
The closest question I can find on this topic is: When to end usability test task but it doesn't address ending a question after a certain amount of time has passed.