In your life situation, a $500,000 policy sounds about right. Given the fact you have student loan debt and a mortgage, it's safe to assume you're in the building stage of life and don't have tons of cash laying around. I'm guessing the premium quote you've received is pretty reasonable?
I was widowed at 31 with 3 kids, and in retrospect (hindsight and all that) felt we were fairly underinsured for the size of our family and the fact that I had stopped working the year before after the birth of our last child. We thought, if we'd thought about it much at all, that whatever insurance through my husband's well paying job was plenty, and I'd like to think we were not complete financial idiots. Who dies in their 30s anyhow? It does hit home when you know someone close to you going through an illness. Sorry to hear about your friend. In my family's circumstance it was a car accident. I did later receive an additional payout through our auto insurance for the UIM motorist claim, which helped.
Social Security is certainly part of the puzzle - I am forever grateful. But even with COLAs it does freeze at the date of death of the insured. So, what seemed pretty reasonable in 2007 is not as great in 2017. We took the Family Max for only the 3 kids, as I knew I'd be working. The surviving spouse can claim, but only if they earn under $16,000 per year, then it dissipates. It does end at the final child's age of 18 (or 19 if still in school) just as college expenses start. This used to go through 22 if in school, but that program went away years ago. To me, this is where the value of life insurance benefits is really valuable. My eldest had a scholarship to an art school, which was great, but for my younger two knowing that there was a stash for higher education would be such a relief. I'm scrambling to fund 529s. If any $$ is saved from the SS benefits, it must be reported to SSA and turned over to the child upon reaching 18 - so I save out of "my" own funds.
Another thought, kinmarg, is that your and your spouse's student loans might discharge upon death. Sometimes yes, sometimes no. However you proceed, wishing you well, and hope this is something that's never needed in any case. I know we all optimize and are spending averse here but life insurance is something you invest in and hope you never need. It really goes against a lot of the things discussed on this forum.