Apple shifted almost three-quarters of a million iPods in the run-up to last Christmas, a fact confirmed by the sea of tell-tale white earphones on every bus, plane and train.

But as the proud owners of these and similar devices rip their CDs, I wonder how much thought they have given to the longevity of the collections they'll spend weeks building. Very little, I fear.

Unless you've studiously been ripping music for some time, the biggest problem facing owners of new portables is the time it takes to build a decent collection from scratch.

Sure, it's never been easier to insert a CD and rip it into compressed audio files but, once you're on your tenth album, let alone your hundredth, the appeal begins to fade.

But it's something you commit to completing because, once your entire collection's ripped, the hard work's done. All that's required is a simple top-up every time you buy a new album.

This is the same process everyone has to go through whether they're building a music collection for a portable, an in-car system or network streaming appliance.

It's a significant commitment in time and effort, yet one many people undertake with the minimum of research. Most start feeding the discs into their computer and let the software do the rest.

While this will produce a compressed music collection, it's not necessarily as flexible as you'd hope. Overzealous compression may have reduced the quality to such an extent that it's only good for use on a portable.

The format may be incompatible with some devices you intended to use later. Even if the format is compatible, you may discover that aggressive Digital Rights Management (DRM) prevents you from using it the way you'd envisioned.

You may have spent several weeks creating a collection that's seriously compromised in terms of quality, compatibility and longevity.

So what's the right format? MP3 is the most widespread and compatible, but it's an ageing technology which isn't as efficient as modern rivals.

Microsoft's WMA can deliver similar sound quality given half the bit-rate, but there are nowhere near as many devices that can play it natively.

It's worth checking the specs too, as several devices claiming WMA compatibility use your PC to convert them into MP3s first. You then have a duplicate collection occupying extra space, while also sounding worse thanks to the required recompression into another format.

If compatibility and quality weren't enough to worry about, DRM tags your ripped files with licences which, while justifiably protecting against mass piracy, may in some cases limit your options for backing up, data recovery or sharing with other devices.

Despite loving the idea of a disk-based music collection, I've held back for reasons of quality, compatibility and flexibility. There's no way I'm devoting several weeks to swapping discs only to find I've backed the wrong horse.

Sure, there's always a better technology coming up, but you want to ensure your current choice has the longest life.

After much agonising, I believe I've found the ultimate audio format. One which combines flexibility, longevity and uncompromised quality: the wav.

Yes, the format which kicked off audio on the first multimedia PCs a decade ago, yet is compatible with a surprising variety of modern devices including the iPod and Slimp3 streamer.

No, I've not gone mad. I understand that the whole point of compressed formats like WMA and MP3 is to make the most of limited storage and transfer mediums, but hear me out.

While most collections were started for modest portables, many people want to stream them to hi-fis where low bit rates don't sound so good. With wav, you've got the best there is.

Being uncompressed, wavs require in excess of 500MB per album, but this poses no problem for today's cavernous hard disks. A 250GB disk costing £150 could accommodate around 500 albums' worth of wavs, and they can be tagged with the same track and artist info we've grown to love with compressed formats.

Building your music library with wavs protects your investment in time, because nothing better-sounding will come along. Don't get me wrong, I'm not suggesting you copy these wavs to a portable, although the biggest iPods could accommodate at least 50 albums' worth.

No, I'd use a utility to batch-convert a duplicate collection into MP3s. If I'm not happy with the quality, I can do it again at a higher bit rate. Should a superior format for portables come along, I can repeat the process, quickly and unattended.

The important point is that the time-consuming aspect of building a hard disk-based music collection is not the conversion to MP3, but the physical swapping of discs. This particularly applies to vinyl record collections which must be recorded in real time.

So if you're going to spend an age building a collection, why compromise? Uncompressed wavs may seem like a prehistoric solution but combine the best quality with true future-proofing. And today's disks are big enough to accommodate a huge collection of wavs, plus a compressed version for portable use.

One thing's for certain: when I finally get round to digitising my entire record collection, I don't ever intend doing it again.