Storage solution

So I got around 500GB's of files that I want to keep for as long as I live.

What is a reasonable hardware that I could use for at least 5 years before any upgrades are needed?
As far as I understand freenas is a thing. I got 2 4TB Caviar red drives ready for a raid, I'd say I need at least 4 bays just in case, not that I look forward on filling "4"TB's...

Any suggestions?

There are a few different approaches you can take.

Quick and cheap and will last a lifetime
One of your red drives, and a pro dropbox account. Just load up your files to the drive and sync them with dropbox. If your hard drive crashes, who cares, put a new one in and download your files from dropbox over the weekend.

Easy and cheap
Use both of your hard drives and set them up as a mirror on your PC (assuming your board supports raid 1). Sync that to dropbox. If one drive crashes just replace it and reinitialize the array, back to normal. If they both crash, download from dropbox. If you want it even better, buy an extra red drive of the same size and set it up as a hot spare so if a drive fails it automatically switches over to the spare.

A pro dropbox account will cost about $120 a year.

The warranty on the red drives are typically 3 years. So assume you replace 2 red drives every 4 years. So lets take this out 12 years for easy math and simply because i doubt mechanical hard drives will be available beyond 12 years from now.

So 2 4TB Red Drives @ $150 a pop brings you to $300. Twelve years out you will replace them 3 times. That brings you to $900. Twelve years of dropbox pro will cost you $1,440. (Assuming prices stay the same. You may be able to find another service cheaper.)

If you decide to build a freenas box to store your files on, your probably looking at a minimum of $400-$500 for the hardware if you go cheap. In the long run if you have good luck with your hardware, going straight hardware with no cloud storage is the cheaper way to go but slightly more risky.

However if you want the "Lifetime Guarantee" you should add cloud storage into the mix. Tornados, hurricanes, fires, floods. That stuff happens and takes all your data with it. Not to mention many cloud storage services offer versioning. So if a file gets corrupted due to bit rot on you local drive, you can restore from the previous version. Or if you get hit with ransom ware and all your files get corrupted, restore them to a previous version.

So lets say you can't afford cloud storage, or your on dial up or satellite internet? Or you just plain don't want your stuff on someone else's server. Mirror the two red drives. Buy a 1TB SSD. Every night run differential backup of your Red drives to the ssd. That way you eliminate any unnecessary writes.

RAID is not a replacement for backing up files. Always have backups on a separate drive, and preferably in different physical locations.

Crazy solution
If you only need read only access to the data, (family pictures and videos, etc.) Burn them to dual layer BluRays, you will need a dozen or so, but the data on there will last forever with no bit rot. Just keep the protected. Ohh... but they only work as long as you have a bluray player to play them on 12 years from now. So its always a game of keeping up with technology.

So the bottom line is you can get away with cheap hardware if you throw it up to the cloud. If you want your files to last a lifetime, back them up. I hope you weren't looking for specific hardware specs on a system, cause I haven't said anything about that. :( I will throw some hardware suggestions up tomorrow as long as nobody beats me to it.

Well besides slow internet...How much can I trust in service as dropbox? Who is to say they will be there years later?