This century is the first to struggle with the challenge of the digitisation of images. It is not the first to deal with the problem of preservation, but selecting and keeping safe photographs that now need decoding adds a fresh layer of difficulty. We can expect the photographs that somehow become iconic to be preserved in perpetuity ... but the rest? Every advance in technology is likely to make formats we currently take for granted more inaccessible, and will often require a fresh decision on what is worth the trouble/expense of conversion. I really should digitise my father's rolls of 8mm film, for I no longer have a means of viewing them ... , mañana, mañana.

But the real problem is with 'undecoded' illustrations. The person who came across 65 glass negatives of (to us) unknown Ansel Adams photographs at a California garage sale in 2010 struck lucky, but at least he could see what he was buying. Buying an obsolete hard drive dramatically decreases already stratospheric odds of finding something of value.

An interesting attempt at a 'local/global' level to preserve the past can be found at http://www.historypin.com (perhaps a suitable site for Smeggy's photograph in this chain?). It relies of course on the continuation of the Internet, the absence of which is unimaginable to most of us today but the future of which is not preordained.

Some interesting underground shots here, mainly from the 1980s: http://spitalfieldslife.com/2013/07/19/bob-mazzer-on-the-tube/

I agree with this sentiment. The usefulness or even necessity of the steps outlined isn't disputed, but (and I suppose this depends on temperament) lists can deaden the experience of learning. Advice I'd have been grateful for at an earlier stage would have been more along the lines of 'when should I select other than AWB in landscape shooting?'; 'will I find myself using hard- or soft-edge grads most of the time, and how do I prejudge the strength needed?' etc etc. This sort of thing is not of course marque-specific. I am sure some of the things on the list I learnt eventually, and more securely, by getting them wrong often enough to annoy myself.

I'm not sure what mindset you see illustrated by my words, nor whether what you say above doesn't get snared in a slight contradiction. My points were straightforward: in my own storage of digital images, I'm becoming more selective. I'm not suggesting everyone (or anyone) should follow suit; I also expressed scepticism (in response to one of your points) that ditching unwanted shots at this stage was likely to leave future historians at a disadvantage.

I don't really see what Vivian Maier's work has to do with it. It is always a risk if you are unrecognised in your own lifetime that survival or not of your work hinges on chance. That is different from a sensible process of selection as you shoot, feasible in the digital age with a facility that was not available earlier.

This is hyperbole in the digital age (and even in the age of mass-produced film emulsions, come to that), where the problem is one of over-abundance, not of rarity. The shot in Dubai may have an antiquarian interest - no dispute there - but historical interest? I don't think so.

I haven't (yet) reached a storage crisis, but the shots do mount up and I can see the sense in trying to forestall one. I find I'm becoming much more selective in what I keep. I generally load everything into Lightroom and then delete a large percentage from disk after viewing. As I climb up photography's learning curve, I'd anticipate jettisoning an increasingly lower (but still substantial) percentage.

With rare exceptions, I don't think we need worry too greatly about historians' need of our photographs in the future.

I think if you get yourself a 55-300 you're likely to get some answers to the questions you are asking yourself. It's not much of a risk. You can sell it on if it doesn't suit you. It doesn't much matter if you don't use the longer end very often, or even at all. If the 50-200 were a better lens than the 55-300, the argument might be a little different of course.

Another possibility, already mentioned, is the 18-135, which would replace your current kit lens and add a useful bit of length.

Lens safely received in v good condition. My thanks to LennyBloke for such a swift and agreeable transaction.

I've been after a 50-135, a very nice lens by almost all accounts. I have been bothered by the (poor) reputation of its SDM -- not all the tales can be urban myth -- but somewhat reassured by discovering that its firmware can be altered in a rather nail-biting procedure to use the screw drive. I have a DA70 and it is a joy of a lens and perfect for most portraiture. In practice, it may not prove that much less versatile, either, if there's space to take a step forward or backward.

Have sent you a pm