I think a mid-long term investment is a good way to look at Steem. Probably more mid-term than long. "Retirement plan" depends on how old you are. If you're 18, then you may suddenly come into some good money if Steem moons in 5 years for example. Then in that case I'd advice you to leverage that cash to do some basic things in your 20's like - Pay off debt, travel, start looking at real estate... etc.
If you're closer to 60, and you're debt-free, then you may be looking at leaving something for kids (if you have any), or finally buying that yacht to sail to that Island near Zanzibar :)
Hahaha Damn! How I wish I was 18!!!! I Could be traveling the world non stop before 30...Aaargh
For Me I am just at the right age to start thinking of retirement, and probably investments IF Steem Moons....I like to be on the Super Pessimistic Side of things though to not get disappointed. WHAT IF IT NEVER MOONS?
Then What?