If you have young kids, check out what SS survivor benefits would be available. They're surprisingly helpful and not mentioned much.
If not, you'll likely end up self insuring, because if one of you dies, the other's living expenses will drop and the money that you were saving to pay for the person who died can now be spent on the survivor. Although single, I don't carry life insurance - my 20-something offspring have enough in their college funds to finish their degrees, and all the money I have saved for my retirement would instead be available to them to transition into adulthood.
If you're following decent money management and have decent luck and are at a decent starting point, you'll probably be FI in no more than 15-20 years. I wouldn't get a policy any longer than that.
I do like the idea of getting two policies - a 10 year now for a larger amount, and then a 10 year policy in about five years for maybe half that larger one. Then you can cancel them in that same order when you figure you have enough self-insurance.
I think I would take the chance and bank on my health up to about 45 or so, but definitely not in my 50s. And understand you're taking on a risk by doing so - I have a friend who was diagnosed with diabetes in his late 30s. And cancers aren't unheard of in the 30s either. You can do everything well and doing so definitely helps, but health problems can just crop up.
At the end of the day, though, term is just really cheap and also fairly price competitive, so I wouldn't spend a great deal of time agonizing over it or shopping it. Figure out how much you need and for how long, use one of the term life shopping websites, pick an insurer with a good reputation, get the policy, put it on auto pay, then move on. Agonizing over it more than that is going to maybe save you the price of a pizza dinner per year, and there are bigger fish to fry.