Shut off valve turning on Plastic Pipe

I recently moved into a new house and all the supply lines are blue and red plastic.

Here is my question:

I had to remove the toilet to do some flooring work and after replacing the toilet and connecting the water supply back to the toilet I noticed that the shut off valve is freely turning to the right and left. Is this normal and OK? I am worried that the connection will develop a leak or worst, blow off and I will come home to a flood. (the supply line is connected and there are no leaks at this time)

Any help would be appreciated.

Thanks,
RJS

The lines in question are PEX and the seal is made by raised rings around the valve. Turning is okay! I wouldn't sit there and spin them for an hour but it is okay.

valve

It is a "quick and dirty" valve that just pushes on. It will not come off by itself, and when it comes time to replace it, it will not come off very easily then either.

Note the barbed connection for the PEX in the picture below. There is nothing to stop it from turning.