How to append or join multiple times a video file (single file) to make a 10hour long video of that same file using ffmpeg? is there a way?
You can use the Windows command line (DOS or cmd) using copy /b 00001.mts+00001.mts K:\Merged.mts as explained in this step-by-step tutorial, where in your case 00001.mts is the identical file repeated over and over again:

https://photography.tutsplus.com/tutorials/3-free-ways-to-join-spanned-avchd-video-files-into-continuous-clips-on-windows--cms-25830

Connecting the same file 6 times instead of twice, you would just replace in
00001.mts+00001.mts+00001.mts+00001.mts+00001.mts+00001.mts