The good news is that on a singlespeed, it'll be harder to knock the gears out of adjustment.
The bearings will probably not fail in a few weeks if they are properly adjusted (which tends to be a crapshoot with these bikes). Too tight can create slightly annoying drag. Too loose can lead to early failure.
A big issue with big box bikes for adults from Wal* and similar places is that the frames and components are sized for an "average person" - generally around the 50th percentile male or female. If you are around that size, you may agree with the fit. If you aren't (raises hand), the bike will be a lot less enjoyable as it will probably be too big or too small for you.
If you have a bike co-op or used bicycle seller in your area, try to look there first prior to committing to the Kent, as you may find something that fits or rides better and may be more durable at a similar price point.