So far so good. Restarts of scene activation, timer works well. Outstanding!
For those having trouble in setup, I want help!
1. Place the script in - C:\Program Files\obs-studio\data\obs-plugins\frontend-tools\scripts
2. Inside OBS - go to 'tools' menu up on top bar then 'scripts'
3. Choose the mode
4. Select the source.
5. Set the timer in Duration (works for show or hide mode)
Then you may want to restart OBS, I didn't have to.
Click on another scene then the scene with the source and watch the magic work.
Note: I wanted different timings for different sources so I copied and renamed the script according to logical naming conventions, example - 'show_car_timer.lua' or 'hide_chair_timer.lua'
Good luck