It depends on the detail work required, for simple enemy sprites I can sometimes make them in no time at all. I dont really time it tho tbh.
I have a lot of experience with enemy sprites so it goes faster then other things.
The more detailed ones like the tortoise and the golem take a lot longer because when it comes to things like shading, I'm just kinda bad at it. I can spend hours just tweaking the shading, or redoing it over and over until it looks ok to me. Not sure why; my head just struggles with it.
It's the reason why I prefer 8 bit :P Not a lot of shading required.
I want to continue on the game someday, so hopefully yeah. I'm just really into learning how to write atm (novels and stuff)