To the OP, unfortunately Samsung has not posted the time limit specs regarding the S10 so no one knows; they can only guess based on past products. I found these stats for the Note 9 and would assume the S10 stats will be very similar if not the same:
3840 x 2160, 60fps: 5 minute limit
3840 x 2160, 30fps: 10 minute limit
2560 x 1440, 30fps: no limit
1920 x 1080, 60fps: 10 minute limit
1920 x 1080, 30fps: no limit
2224 x 1080, 30fps: no limit
1440 x 1440, 30fps: no limit
1280 x 720, 30fps: no limit
4K video is awesome but it is very taxing on the processor and generates heat quite easily. With no venting there are typically set time limits to protect the hardware from being damaged.