Your preamps probably do run a bit hotter when the supply voltage is higher.
This is because the higher supply voltage translates to a higher voltage coming out of the power transformer into the rectifiers and power supply reservoir capacitors.
That means that a higher voltage is being applied to the preamp power supply voltage regulators, which must then be dissipated as heat. (This is assuming that the preamp power supply is linear, as opposed to switched mode).
The increased heat will be largely generated by the preamp voltage regulators, not by the preamp circuitry itself, since the voltage supplied to the preamp circuitry will be... regulated.
Looking at the math: 130V is about 8% over spec and 113V is about 6% under spec.
This will translate to a couple of volts variation each way on the rectified and filtered voltage applied to the preamp regulators. That should probably be OK, if the on-board voltage regulators have good heat-sinking.
Anyway, the above doesn't actually answer your question
but perhaps is something to think about?
You could look at something like a Furman regulator :
FurmanSound.com - Pro A/V Product - AR-1215
but note that the regulation is ±5VAC which is pretty close to what you already have...
Hope this helps!
Paul