I'd like to avoid, if possible, it getting slower with age...............I use Revo Uninstaller Pro to uninstall programs so there is no left over crap in the Registry..........I clean out my temp files and browser history at least once a week. I use AVG for an anti-virus program and Windows build-in firewall. I also use several programs to frequently root out malware..........I run chkdsk regularly and defrag also (although I've heard that it does no good to defrag an SSD)............if someone out there can make some suggestions that I haven't thought about, please let me know. Also, I'd like to avoid ever having to perform a clean install since I have so many programs installed. Windows 10 is coming out and I'm also looking for advice as to whether or not I want to install it over my current Windows 7 installation.
Sounds like you've got it pretty well under control and have good habits.
I would not expect registry crap to affect speed unless you have VERY extraordinary circumstances.
No, don't defrag SSDs.
Keep an eye on your non-Microsoft services as seen in the services tab of msconfig.exe. They have a way of growing. Also keep the startup programs checked on the startup tab of msconfig.exe to a minimum.
This is an area that I have yet to learn. If I add an app and it has a service attached to it, how can I avoid having the service added the startup? Also, some apps are designed to work at boot. Do you have any advice about this? My boot time is almost 5 full minutes. That's intolerable long - yet, I don't know what to do about it. I want the startup apps (although, many could be delayed - but I don't know for how long. The same goes for some of the services. If I delay these items from boot, what happens to the speed of my computer when they kick in? I really need help in this area. Can you help?
I haven't done a clean install since I built this PC in early 2011. It's as fast as ever. The only issue I note is that reboot time has crept up by 10 seconds or so, despite my efforts to keep things ship-shape. A clean install might solve that, but that's a huge step to take for little and possibly no benefit.
With any luck, you won't have to do a clean install until forced to by your next upgrade. I do clean installs any time I change motherboards (almost never), but there are programs such as Paragon Adaptive Restore that will at least attempt to get around the problem of new motherboards and chipsets.
I assume you use some sort of imaging program and keep at least a couple of images--maybe one done shortly after you got things properly configured and others from later periods as time goes on.
Avoid the temptation to use a bunch of magic utilities or suites that claim they will refresh your PC or ensure its health. I'm not sure what you are now using, but I'd get antsy if you went beyond CCleaner, maybe Revo, and whatever is built into Windows. I used Revo for a while, but have heard of issues and am frankly unsure it does anything that measurably improves performance--though it would clearly make you feel better for "being clean" and save some miniscule amount of space. Mebbe you're better off just taking a shower to feel clean and instead rely on the Windows uninstaller.
Win 10 is too much of an unknown at this time to judge. I'm undecided myself what I will put on a new PC I plan to build before year end. Win 7 will be supported until 2020.
The major issues surrounding Win 10 to me are the nature of the licensing, the details of the "free upgrade" offer, and how it will be updated and upgrade over time. If the only issues were its functionality and the interface, I'm sure I could live with it---but the unclarified details may be a show-stopper. No way to judge that until Microsoft starts talking.