Short-term mortgage vs. longer-term mortgage - which one?

Regarding term, take a term today based on your expectation of available rates at renewal time. This is called your "renewal risk." For example, at the time of writing...
- An ultra competitive 2 year rate today is 2.34%* ... question to ask is what will the rate be on a 3 year term at renewal for an apples-to-apples comparison with a 5-year fixed rate at 2.94%. The break even point is 3.29%, so you'd be better off today with a 5 year rate if you have to renew in 2 years at a rate higher than 3.29%
- An ultra-competitive 3 year rate today is 2.59%*, so you would need to renew for 2 years at 3.53% or less to make the 3 year term worthwhile. (PS - I use a fancy spreadsheet to do the math!)
- Keep in mind, no one really knows where interest rates might be. Personally, I just took a 2.94% for 5 years myself. Set and forget...I know what my payment is for next 5 years, and I see it as a coin toss.
- Alternately, if you want to play the short game and fret about the market, you can take a variable rate mortgage for now and lock-in a fixed rate if you start to get concerned. A 5-year variable rate today might be Prime (mortgage) Rate less 0.50%, so 2.50%, maybe you can get it for a touch less. (* note: some first time borrowers get confused or focused on rate when the REAL GOAL is to get approved by a lender. Ultra-competive rate might not be offered for your employment and/or credit profile.)
- In today's market, I feel 10 year terms are generally noncompetitive (4.29% at present), paying far more today for the "potential" that rates might rise a lot. Doing the 10 years at 4.29 vs 5 years at 2.94 math, your break even is 6.01% for renewal, meaning a 10 year contract would only make sense if you felt 5-year fixed rates would rise above 6% by renewal time.
So that is how to do the analysis. If you need help, please contact me.
