Another tip I can offer.
Earlier this year I received an email from an airline I travelled with approximately two years ago saying that I have points expiring about a month or two later.
The airline was Etihad. I do not have any loyalty to one airline, I go for price and convenience when travelling. So, I don't really accumulate a large number of points with one airline.
Anyway, I went to their website to check out their online shop. There was nothing I could see that I really wanted or needed. Nearing the end of my perusal of their site I found you could exchange the airline points for Amazon gift vouchers.
Firstly, I transferred my wife's points to my account giving more points to spend in one transaction, then I exchanged the points for Amazon gift cards. By doing this it opened up a much larger range of products to obtain.
I ended up with a few hundred pounds sterling worth of Amazon gift cards.
If anyone has points which may be expiring and you are not likely to use them for travel, check out other options I have mentioned.
Great tip. Not accumulating large miles with one airline is important if you aren't diversified or don't travel a lot. It pigeon holes you. This is where transferable points - like Chase UR or Amex MR really come into play. They are naturally diverse and worth stockpiling.
If you KNOW you won't be traveling in the near future and your points will expire, it's better to spend them on something.
Remember too that airlines have partners. Etihad specifically partners with Air France, Air Canada, American Airlines, KLM, Jet Blue and many others. As such your points are much more diverse than it may seem at first glance.
What others may not realize is that almost all airlines only require SOME SORT of point exchange to re-up your miles for another 2 years (or whatever the point expiration for that airline is). That typically means simply spending miles on a purchase or buying a small amount of miles extends the expiration of all of your miles.
Using miles to buy gift cards such as you did can be a real option, though it's typically not the best use of miles as you'll typically get only $.01/mile at best out of that type of transaction. My goal is always to maximize those points through partners and diversification.