Did I make a mistake in Financing? How long do you finance?

You got what you got. Enjoy the camper. It should last with proper care.

I do recommend investigating a refinance. I do not know your loan value, but you might be able to get the loan term and interest rate lowered saving you money over that 12yr period. For example 10 yr at 5.25% is very close to the same payment. Find out what you might qualify for at your credit union for 8-10 year loans.