Winclone 6 or later is able to clone and restore your Boot Camp partition in either file-based (WIM) or block-based format. File-based imaging can be slower than block-based due to the large number of files and the number of file operations when cloning and restoring. If you have a Mac with a physical disk versus a SSD drive, writing data can take significantly longer. If you are saving to an external drive, the speed of the bus may cause slowness as well (USB-2 is slower than USB-3, etc).
In our testing, it usually takes about 2 to 5 minutes to restore a 20 GB Winclone image on a MacBook Air with an SSD drive.