I'm naturally cautious and careful. I don't like to make rash decisions, I like to carefully weigh my options and do the right thing. I'm very keen to get the very best value for my money, doesn't matter if I'm buying something cheap or expensive I like to get the best value.
Nearly 7 years ago I bought a pair of DNUK desktop computers running Debian. They have been very good and with upgrades have kept going very well over the years. The moving bits on them are now coming to the end of their natural lives, I've lost one PSU and a DVD player already and the CPU cooling fan is a bit noisy now. Their old AGP graphics cards are clearly not up to modern standards and while the single core AMD64 processor was fast when new - they aren't that fast anymore. A new quad core system, with four times as much RAM and faster RAM at that (DDR to DDR3), new graphics and larger faster disks isn't that expensive. I will replace them with the next 18 months - the dilemma is how long to wait to get the most out them and the best new versus a sudden failure and the fact they do feel slow now...
In the same token I have a more expensive dilemma. We bought our house 2 years ago. We knew that the boiler would need replacing. The solar water heater is home made and not to modern standards nor is it linked to the current gas system. The solar system isn't performing well so the current dilemma is when to rip all the antique junk out and replacing it with a modern high efficacy condensing boiler, versus carrying on as we are - again accepting that there may be a sudden failure.
The annoying this is that I know in some respects the £3000 we spend on a boiler would be paid off by the reduced gas costs over 10 years. Just as I know the increased productivity from a faster computer would help (well only a little),