Need more advice on overall back up strategy

Question

Based on my previous post, "Need advice on setting up a portable external hard drive", I set up a portable backup strategy for the iBook G4 consisting of a 250 GB hard drive in a firewire enclosure which contains two bootable clones. In a similar fashion, I set up a 320 GB drive in a firewire enclosure which also has two bootable clones and also an empty partition for the MBP.
Also, I have a 160 GB La Cie firewire desktop drive that was purchased in November of 2006 which has Time Machine and some other backups on it, some of which are unique.
Since I had to dig pretty deep into the piggy bank to buy the drives and enclosures, I really don't want to buy any more hardware for a while. I also didn't expect I would have to worry about archiving anything for a while since I thought I had lots of capacity, so I hadn't intended to post this question for a while. However, circumstances have changed rather suddenly.
After getting the logic board reballed and replacing the original 30 GB hard drive with the 120 GB drive, I decided to give the iBook to my rather cyberphobic Significant Other, along with a red iPod, a DynoScope, and the 250 GB backup drive as a first computer, little realizing what was about to happen. Even after 27 years of marriage, someone can still surprise you.
My SO started digitizing our music collection, and once all the CD's were put into iTunes, started in on the vinyl collection. The iPod is already full, and both cyberphobia and hard drive space are rapidly evaporating. The vinyl files seem to be much bigger than the CD files. The 120 GB internal drive and 250 GB external drive that seemed so huge is now beginning to look too small. The overall strategy is still fine, but I'm about 60 GB's away from having to archive some of the music collection to free up more hard drive space both on the internal drive and on the backup clones. On general principles, I would rather do the archive on a third drive, and this drive does not need to be portable.
I do have quite a bit of excess capacity on my MBP and MBP backup drive, and perhaps this could be utilized in the short term. I could use the La Cie, but the problem is that an archive would likely use up most of the free space remaining.
So what I probably need advice on is what to plan on setting up that will accommodate both computers. The iBook is running Tiger and has iLife 06 on it. The MBP has Leopard and is running iLife 08. I already know that if a photo is in iPhoto 08 it cannot be put into iPhoto 06. I don't know how it works with iTunes--both computers seem to have the same version of iTunes--v. 7.6.1. So I don't know if the iBook needs to have a separate drive or if it could use the same drive as the MBP.
Also, I am wondering if there is any way of finding out about impending failure of an external hard drive since S.M.A.R.T. status is not supported. I can verify the disk using Disk Utility, but was wondering if there was anything else to do other than pay attention to how old it is and how noisy it is. I imagine it is still true that over time, all hard drives will fail.
Would setting up a RAID be something to consider? Does that give some protection against the failure of individual hard drives? (I don't know much about RAIDS.)
I apologize for the length of this post. I wanted to try and include all the relevant information about my situation. There seem to be so many possible options that I am in a real quandary about just what to do, both for the short term and for the longer term. But I would like to have a sensible long term plan worked out in advance, so that when the time does come to buy more hardware, I will have a clear idea of what to get and how best to set it up. Any advice and help will be greatly appreciated.
Thanks in advance!

Answer 1

Thanks for responding!
You are right about the AIFF format. I will have to burn the DVD's on my MBP since the iBook can only burn CD's, but I don't see any problem about doing this except for a question about DVD's.
I have read several times about CD's degrading over time so that the data is lost and the CD's just turn into little gold frisbees. I think this is mostly true of the super cheap store brands, and I don't know if it's also true of DVD's.
So I am wondering about the projected life span of whatever DVD's I choose to burn onto, and also, how best to store them. I have a stack of Verbatim DVD's which are supposed to be a good brand, and I have a much smaller stack of Archival Gold (by Delkin) which are supposed to be good for 100 years. 100 years is probably in excess of what we really need, but I would like to think in 10 or 20 or 30 years, the DVD's would still be good. If not, then I just need to know how often to reburn them.
I tend to worry about the longevity of digital media. I had burned the iPhoto library onto inexpensive CD's, and used these to put it on the iBook. On every disc, there were unreadable files. The iBook can't read one of our purchased CD's, even though we have played it many times elsewhere. We'll try it on the MBP and another external CD drive that we have to see if we can digitize it.
I think the DVD's for the large vinyl files are a great idea and I will plan to start doing this at some point soon. I will also burn either CD's or a DVD of anything which is an only copy. Right now there aren't many of those, but of course that could change and probably will.
I can see we need to sort a few things out, but I think the road ahead is much more clear now. I addition to the original CD's and DVD's that I plan to burn, I will probably still keep redundant copies the entire iTunes library on a couple of different hard drives, since I have a lot of capacity open on the MBP. The music itself will be well backed up with discs, but since it has taken so many hours so far to put music into the library and will take many hours more, I also want to be sure in a way to back up those many hours of effort.
Thank you very much for all your help. I want to keep this topic open a bit longer in case my SO has any further questions, but I think my concerns are pretty well answered.
Many thanks again!