I don't own a Lifecycle Fund.  Your post sounds like you're near the beginning of your career.  It's very sensible to get started on investing without waiting to learn all about it.  The sooner the better.

I'll observe that you may have many employers with many different plans by the time you retire.  Some of your plans will get rolled over or combined (at your choice, I mean), others you'll find so attractive that you'll want to hold on to them even though it makes your record-keeping more difficult.

Originally, Lifecycle Funds were conceived of as a one-stop choice.  That is, they were intended to be someone's entire investment at a fund company.  But the way investing and marketing is today, it's very hard to persuade a customer to stop with one fund.  My point is, suppose in five years you get a new job, and that the US economy runs poorly for the next five years?  Your Fidelity or TIAA-CREF lifecycle fund may also be a disappointment.  But it probably will have done exactly what it was promised to do: Invest mostly in stocks, and buy more shares with your periodic payroll contributions while the market was down and fewer shares while the market was up.  You'll look at it and think, "Maybe I made the wrong choice", and you'll roll it over into the new employer's plan, with a new set of choices.

So one issue is whether your desire to make a prompt decision reflects your ability to disregard short-term fluctuations in your retirement account, and keep your hands off it. I'm not arguing with you, just asking you to think about what your risk tolerance is, and what your reaction to a possible U.S. economic recession might be.

You would have to learn a little about investing to make the other choice, two or three funds that you hope will have different performance characteristics, so that you'll see (when they go up and down) that you don't have all your eggs in one basket. Unfortunately, two of the most special choices at TIAA-CREF, TIAA Traditional and TIAA Real Estate are the hardest to understand.

I don't usually find Fidelity to be the lowest-cost provider, but it might be useful to find out if the Retirement-plan status gets you some of their especially low-cost funds without having to get the minimum amount in the fund you'd need in a plain retail account.  They certainly have a fund for every purpose (!), but you probably just have 15 or 20 available in the retirement account.

Tim