[Bill Harris]

In my opinion, I think it depends on where the device controlled resides in relation to the power source. On my car (stocker), I have a battery in both the front and rear of the car. So for my fuel pump which is mounted in the rear, the relay is also in the rear and switches power taken from the switched side of the cutoff switch though an in-line ATO type fuse. That keeps the total length of the high current circuit as short as possible. The relay control line, which is small gauge and low current, is run to the switch bank by the driver. Likewise, the fan and water pump relays are mounted up front, using the high current available at the front battery and sourcing through in-line ATO fuses. Once again the small gauge low current lines are run to the switch panel. You can supply all of the relay control circuits through a single low current (2 to 5 amp) fused source.

If you locate the relays in a single place then you wind up running heavy gauge wire all over the place. It's a lot easier to run 18 or 20 gauge relay control wires to a common point. The relays themselves should never need "servicing" as long as you are using high quality automotive type parts that are rated at least 2X the anticipated load (i.e. 30A relay for a 15A load).

That's my 2 cents anyway!