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This thread is more than 5 years old actually.
In all those years 9 volt batteries have never given cause for extra wear let alone problems with motors or any other components from these cameras.
First of all these cameras are built like a tank and have quite a lot of reserve capacity to cope with any extra strain should that occur.
Secondly the 9 Volt from those small block batteries drops to a considerably lower value as soon as this battery is loaded with the motor of the camera.
I have used the 9 volt alternative quite a lot and have never exerienced any problems with he 500 ELX camera it was used in.
The 9 volt battery is the only alternative readily available from filling stations and other non camera shops.
Finally there was a mains power supply available once from Hasselblad for the EL series that also supplies a higher output for these cameras.
As far as I know this was never the cause for extra wear.
Please get your units right: current is indicated in Amperes, voltage is (obviously) in Volts.
The motors in the EL cameras are not flimsy parts, and do not suffer from premature failure from a 9V supply. The motor draws quite a bit of current which makes the voltage of the battery drop considerably. The internal resistance of a 9V battery is much higher than a NiCd rechargable that is in good shape.