doesn't Mac have some tune-up utilities or at least analyzer which points out to issue areas? I know Mac is supposed to be used not tuned but still, HW & SW are all similar, over some good years freshly installed OS (if it's not too new for old mill) is what helps.
There are plenty of apps on the market designed to help a user manage and administer their OS X system. I've never used any of them as they are mostly unnecessary. The basic principles are very easy:
- Keep 25% (or at least 100G) of free space on the system startup drive
- Put large data files (like video, music, and photo repositories) on external drives when needed to keep enough free space on the main drive.
- Leave the system plugged in and running, asleep, overnight a couple of times a month. OS X has some background cleanup tasks designed to minimize fragmentation, etc. These tend to start up and run in the wee hours of the morning when it is expected that users are not using their system.
If you do those things, and keep the operating system and apps up to date on revisions, your system should always operate well and should never "slow down" simply due to age.
There are, of course, other strategies for data organization and application use that can optimize system operation, and, of course again, a particular system can only perform as quickly and with the capabilities that the specific hardware configuration allows at the limit.
When I buy, I try to buy everything a system can manage at the beginning on the basis that this way I get the most performance and the most use (value) for the longest time with a given system. When newer models outperform what I've already got by enough of a step that it's worth it to buy a new one, having a max'ed out system of whatever type that isn't too too old to still have some life left has greater resale value than either a system that's too old to have any future or a minimum system that has a little life left. My experience shows that this upgrade with Apple gear seems to be about a 2-3 year cycle, so if I bought the extended warranty, my systems are always covered by warranty AND there is additional warranty to transfer to the new owner if I upgrade in the third year ... another improvement on resale return.
Na, I didn't think this out with foresight, but hindsight is pretty clear. ;-)
G