(SPLG) let it sit for 50 years and you'll be ready to retire, I'm not invested but would be if I was a young adult. Factors determine your retirement level like how much you invest is key. Now, I started with $390.00 \~12 months ago using (GLD, AMZN, QUBT) and now have $1,920.00 and growing; that's about 33% interest...It's an experiment I'm doing in the stock market. Not great but way better than a bank savings account; it's like getting paid $128.00 a month.
P.S. Best advise you can get is find yourself a good Financial Advisor Fiduciary.