The only way to find out for sure is to try it for a while, say several days, all the while monitoring the state of the system and the applications involved.
It is certainly possible to leave a pi on indefinitely, doing various things. If you are playing a video, you may run into a problem with the display going to sleep, but that is a different question, and a bridge you can cross when you get there.
By "monitoring", I just mean checking in to see that the resource usage of the system, primarily RAM and CPU, remain constant while the system is doing the same thing over time. Beware that total RAM usage may increase gradually all the way to 100%, but this is not the same as the total RAM used by processes. It includes some kernel "buffers and cache"; there are many explanations of this online, particular WRT the tool
free, which clearly shows the difference.
A few years ago I wrote a simple command-line client-server application for monitoring specific processes over the long term (as in weeks and months) in a style similar to
top. It can be compiled and used on the pi.
You want to make sure your key applications maintain a stable profile, memory wise. If not, this would likely indicate a leak, which will build up over time and eventually crash the application if not the whole system. You also want to make sure they are not prone to over-taxing the CPU, although that problem is easier to deal with.