How much storage space does one need? And in what arrangement?
A very subjective question. Personally I have a 256 SSD and a 1TB SSHD in my rig + a 1TB storage NAS. That's plenty for me, but for some, that's tiny.
I get by fine with a 60gb ssd boot drive and a 500gb store drive but some just like to download ron jeremy's porn collection to there pc's.
If i dont need something or am not playing a game anylonger it gets deleted its just going to depend on you.
I have in my main gaming system 1TB SSD
I have 500GB in my second gaming system
I have 6TB in my NAS
120GB SSD and 1TB HDD.
All of it.
the 100 PB data center of Google would probably last me a few years.
pretty much.
Get as much as you want and when it reaches 60% full, start planning to upgrade. Some filesystems (zfs im looking at you) start to get snarky when more 80% full.
Also how ever much you get, make show you have a sane way to back up and restore it. Never have more data then you can look after.
My current system has a 120gb SSD for the OS which I think I need to upgrade to a 250 becuse windows just keeps getting bigger. and 2 1tb WD Blues in Raid0 with another 2 1tb WD Blues in raid0. Keeps my machine fast on a budget. Then I have a 24TB RaidZ file server with 6 3TB and 64TB drives in 4 pools of single raidz. It may sound like overkill for redundancy with those drives. But the advantage is I was able to slowly build the system. Started out with just 1 pool of 3 3tb drives, then added 3 more 3tb drives, then the 3 4tb drives and so on. So I was better able to stagger the purchasing of the drives and upgrade it as necessary without having to rebuild with each upgrade.
So in the end enough storage space depends on what you need and what you can afford. FYI there is nothing on my desktop that I cant afford to loose but is all on my file server which I access over gigabit network. Cant wait to upgrade that to 10g eventually.