This is a very busy time of year for me with merchandising jobs. One of the reasons is that I do cosmetic resets. There are a ton this time of year!
I work for multiple companies. The trick is to find jobs that work well together. I have one that is consistent (almost) year round work that is not locked in to specific days (so I can flex it around a bit).
The cosmetics resets are heaviest this time of year and then again starting in June. 4th quarter is very slim for that kind of work.
I have a WM dedicated job that is pretty consistent but can get busier 4th quarter.
I also pick up some project work as filler on occasion.
Can you work full time hours with merchandising....yes, and you can do it with one company or multiple companies.
Good luck in finding your perfect balance of work!