Is the second job going to be a long term venture or is it just for the holiday season? Is it something you would enjoy doing or something that has perks such as good pay or learning a new skill or something that would help you reach your long term goals, whatever those may be?

How many days per week would you be working both jobs? I used to work 12 hour shifts at a single job and I'd pick up overtime sometimes but every fourth week I worked the weekend and had the rest of the week off so I was able to recharge by looking forward to the long stretch off once a month.

I despise morning shifts too. I prefer night shifts.