Before buying anything to treat something you should verify what it is that you need to deal with.
Have you seen any insects running around let alone any spider mites?
I’m sure the art of war had something relating to this concern.
If you do verify that there are spider mites present there are many…many…many…many products available and Neem is ok but I wouldn’t treat for anything until I verified what it was.
Nature develops problems slowly and you should not take the knee jerk reaction but evaluate things to make the best decision based on the facts at that time.
Want to read some info on battling spider mites?
I still have them and am reusing my old soil and pots doing no till grow and I am now using predatory mites to keep them under control.