I am not an expert on this, so wait until some more experienced users (like Tpartner & Denis) will skip in. However, in my experience, everything that has to do with web technology is generally always quite "unstable" when it comes to response time. You still have http and database connections, that might take sometimes longer, some times are quicker.
I guess when experiments are time sensitive, they should not be dependend on database connections, etc. You might be able to run them purely in the browser (e.g. via Javascript, Flash, etc) and only at the end transfer the timings etc. This is probably better when treating time sensitive experiments. But even then, with Javascript, at least a couple of years ago there were significant differences between the speek of how browsers rendered javascript code (if I remember right, Chrome was especially quick in doing so), etc.
Of course, with the same machine and browser, etc. this shouldn't impact too much, but I just wouldn't want to rely on it.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
No support via private message.
The topic has been locked.