@Connor McGinnis
It is more of a lifestyle choice. What do you want: more or less debt? It seems that your parents prefer less debt, which is why they like their loans to be amortized over a few years. Essentially, a shorter term allows them to pay off their debt more quickly. That is a fine approach and is more conservative.
However, for my preferences, I would focus on optimizing debt for cash flow. I want my interest rates to be as low as possible and my loan to be amortized over the longest period, typically 30 years. This allows my loan payments to be smaller and my properties to be more profitable. Additionally, a longer amortization period provides more flexibility. If you have a 15-year term, you're forced to pay it off quickly. However, with a 30-year term, your mortgage payment obligations are smaller, but you have the option to pay more toward the principal if you choose.
If you’re having trouble penciling things out, it could be because you’re using an atypical debt structure. Many investors use 30-year terms.