I already answered to this question in your ticket. However, i will post the same answer here, so that others from the community can find it.
I tried to reproduce your issue with our latest official release on our side and it seems that the code works as expected. It takes about 360 milliseconds to load a RadSlider
control with Maximum
property set to 4000. Can you please take a look at the attached project and see if I miss something. It will be great if you can change the code according to your scenario and send the project over. By doing so we will be able to further investigate the reasons behind this behavior.
Pavel R. Pavlov