z80.eu: Schmoburger, MJ313, Uni and others have provided some very useful information on this thread (not to mention the forums altogether). I think the general argument is that in replacing all of the caps, you will have eliminated bad caps as your culprit. The fact of the matter is, those electrolytic caps will (or have) fail(ed). The IIci, from what I've read, is notoriously bad in this respect, though all Macs of a certain age will have this problem (and it applies to the motherboard, power supply, analogue board, etc.).
Basically, you either sit on two sides of an argument regarding the collection of old Macs: you either think they should be left how they are, which might mean they degrade, caps leak and they cease functioning OR you acknowledge that maintenance is required in order to get them running. There's no inherently wrong position, but if you're in the first camp and also expect the Mac to continue functioning, you might be setting yourself up for disappointment.
I come at this from a position of being relatively new to the restoration of old machines (Uni can attest to my amateurish cap replacement style). What I will say is that in a single case in which bad RAM was my problem, every non-functional or semi-functional machine I own has been made operable by removing old caps, thoroughly cleaning the board (usually with 99% isopropyl alcohol and, in one case, the dishwasher), and replacing the old caps with tants or ceramic ones. New electrolytics are useful for the PSUs and analogue boards and the occasional axial replacement. The only machine I haven't got working using this method is an SE/30, which I totally screwed up during a bad recap session. So, that's my fault. Could you have another issue? Sure. Why not? It's a piece of nearly 30 year-old technology. It's worth putting at least some stock in what these people are suggesting, though, because experience is on their side. When you've replaced all of the caps on the motherboard (and cleaned it), and arguably those in the PSU, then maybe come back with whatever problems your machine is still exhibiting. Hope it goes well!
Basically, you either sit on two sides of an argument regarding the collection of old Macs: you either think they should be left how they are, which might mean they degrade, caps leak and they cease functioning OR you acknowledge that maintenance is required in order to get them running. There's no inherently wrong position, but if you're in the first camp and also expect the Mac to continue functioning, you might be setting yourself up for disappointment.
I come at this from a position of being relatively new to the restoration of old machines (Uni can attest to my amateurish cap replacement style). What I will say is that in a single case in which bad RAM was my problem, every non-functional or semi-functional machine I own has been made operable by removing old caps, thoroughly cleaning the board (usually with 99% isopropyl alcohol and, in one case, the dishwasher), and replacing the old caps with tants or ceramic ones. New electrolytics are useful for the PSUs and analogue boards and the occasional axial replacement. The only machine I haven't got working using this method is an SE/30, which I totally screwed up during a bad recap session. So, that's my fault. Could you have another issue? Sure. Why not? It's a piece of nearly 30 year-old technology. It's worth putting at least some stock in what these people are suggesting, though, because experience is on their side. When you've replaced all of the caps on the motherboard (and cleaned it), and arguably those in the PSU, then maybe come back with whatever problems your machine is still exhibiting. Hope it goes well!