What will you need the life insurance for at that point? Would you be able to save $10,000 in a savings account between now and age 70 instead of paying for whole life insurance? If you take the $26.50 difference in premiums that you mention here and put it into a savings account each month, you’ll have about $7,782 by age 70, assuming 1.5% interest. If you can increase that monthly contribution to $34.25, you’ll reach just over $10,000 by age 70. And that money will be available for whatever you or your family need, any time you want.
Any reputable source will report mutual fund and stock returns as “annualized” figures, which takes the sequence of returns into account. Another term for this is “geometric average”, which again accounts for the order in which returns are received. So while there are some financial “experts” out there touting average returns (cough, Dave Ramsey), for the most part what you’re talking about here is not a factor.