On the one hand, if it's not broken, why fix it? On the other your A1200 is over 20 years old, and if there is one thing we know for certain regarding those little electrolytic caps inside our Amigas, it is that they will fail eventually.
Already there is a chance they've dried up some, and are leaking current. Caps are designed to do three things: store a bit of energy, block DC and let through AC. So a 'leaky' cap, one that lets DC through at low to no resistance, can at some point decide to cause a direct short to ground which spells all kinds of bad things for your system.
What is a bit annoying, is that unlike say diodes, resistors and transistors, testing caps in system is just about useless. You can only really check for direct short, and even that may give a false reading as you might pick up a signal that takes another route between your probes.
So the alternatives are to assume your caps are good for a while more at least - and change at first sign of your Amiga acting up - or play it safe and just change them now.
When changing by the way, there is no rule that says you have to change with new electrolytics. On the digital only part, Ceramics or Tantalums will last forever. For the Audio circuitry though, electrolytics or oscon caps will yield the best quality - though you could use Ceramics as well if you're not that picky about audio quality.
(One word of caution though: If using Tantalums - triple check you got the polarity right. Get it wrong and they might just explode and burst into flames...)
