Agreed, it seems pointless to sink a load of money into an amazing PC build only to let neglect and poor maintenance destroy your hardware. Plus, when you consider the dangers of an overheating CPU or poorly maintained power supply you really are risking more than just your pc - electrical fires are real.
If you are a noob, articles like this one are a good way to learn what kind of regular maintenance you should be carrying out for specific hardware - and some advice I have had for every friend who has ever looked into building their own pc has been to buy compressed air as soon as possible, just to prevent dust build-up - such a simple bit of maintenance that can pay off drastically when it comes to temperature control.
Saving downtime is so important to - yes it times consuming, but more importantly, repairs and fixes can go wrong. Massively expensive PCs can sit bricked for ages just because an easily avoidable bit of upkeep was neglected.
Clean out them cases!