The scary thing is, the newer the gear, the less likely it will be to work in the future.... some reasons:
1960s - The earliest synths were made using discreet components, assembled by hand. If something fails, chances are a good electronics guy can fix it.
1970s - Still mostly discreet components, microprocessor chips appear, but these can be still be replaced today, if you can find one (e.g. CEM, SSM chips)
1980s,- integrated circuits - which means it's no longer possible to repair - you have to source a chip or a replacement circuit board.
1990s - integrated circuits are even smaller and more manufacturer-specific. Software drivers, editors etc. will not run on modern computers.
2000s - combination of the ban on lead solder and the continued shrinking in size of integrated circuits leads to the problem of tin-whiskering, which will kill your gear! http://www.theguardian.com/technology/2 ... ngineering
2010s - by now, some gear actually needs software running on computers (e.g. Nord Modular). In future, the software is no longer supported and the computers and the operating systems they use are obsolete. You can keep an old computer, yes. Did you read about tin-whiskering? Dammit.
Even those people who moved over entirely to software synths (VSTs etc.) will one day find their favbourite synth is no longer supported, and the computers they need are dead.
The moral of the story is: KEEP BUYING NEW GEAR!
Agreed... if you have the money!