I have a system that more or less works for me, although I will admit it has evolved quite a bit over the years due to some mishaps and misfires, but basically it involves categorizing my projects based on the probability that I will need to edit them again, including the level of editing that might be required in the future. It’s essentially a risk assessment. Your own risk assessment will of course be different than mine.
Categorize project step 1 – amount of detail needed to archive: group/bus level, track level, or fx level? (I’ve found I can get away with different level of detail needed, depending on the client, situation, contract, etc.) Group/bus level is the easiest obviously… all the way to FX level being the most nightmarish to archive.
Categorize project step 2 – timeframe needed: how much editing is likely in 2 years, 5 years, and 10+ years? I’ve found those timeframes to line up with compatibility/ease of restoration for me re: OS issues, major DAW changes, major plugin changes, etc…
Based on the categorization and risk assessment process, I do entirely different things with them on a sliding scale of effort:
For simplest archiving, I will simply bounce out logical groups/stems/buses and maybe a couple of critical tracks like edited lead vocals, for example. That’s it. Cross fingers I don’t need more than that. This logically scales all the way to meticulous, surgical exporting of tracks, including wet/dry, and critical fx in case I need them. This takes a long time and is a pain in the !#$@#%@#.
In ALL cases, I of course keep the actual project and source/raw files AND I try to keep backups of almost ALL of my most important plugins in case I have to try recreate a DAW environment of some time in the past. I still have old backups of almost every OS installer, DAW, plugin and library I have used going back 15+ years. I figure if I have to, I can go on EBAY and find someone willing to sell me some ancient old computer if I absolutely need to. Cross fingers that never happens.
I have learned to be more selective with which plugin developers to trust longer-term. I have made some poor bets in the past and have been burned. Heck, I’ve been burned by DAW developers too. So I’ve tried to keep my DAW much more simple these days… I’ve consolidated around fewer developers I like, and hope they stay around for a long time. I have accepted the idea that “less is better.”
Lastly, I have a pretty robust backup routine… I use the 3-2-1 backup methodology for just about everything.
It’s not a perfect system, but I treat my projects/content like a business (because it is a business) and it takes time and money to do it. Any time I have slacked off (and I have indeed slacked off a handful of times), I have invariably been burned. YMMV