Light bulb lifespan changes exponentially to the power -13 (negative 13) with input voltage. Let's do some math.
Take a bulb rated 500 hours at 12.8 volts. Put it in that vehicle. We probably aren't going to run it at 14.5 volts, because there's going to be some voltage drop along the wires and switch contacts, but the bulb could easily see 13.8 volts.
(13.8 ÷ 12.8)^-13 = 0.376. Our bulb fed at 13.8v will lose over 62 per cent of its rated lifespan.
0.376 × 500 = 188 hours.
Voltage regulators are temperature-compensated, too, because a cold battery has higher internal resistance than a warm one, so it needs higher charging voltage. What's this 14.5v going to turn into next winter? I had a car ('91 Dodge Spirit R/T) with the voltage regulator built into the engine control module. Its temperature compensation was faulty, such that when it got cold out and the car had been sitting a couple hours so there was no heat in the engine bay, it drove charge voltage as high as mid 15s to low 16s. If I didn't let the car run long enough to warm things up underhood a little so the voltage regulator would back off a bit, turning on the headlamps resulted in two bright flashes and no more light from up front until I put in new bulbs; the dead ones had little globs of tungsten at the filament ends. All caused by the overvoltage.
Okeh, a turn signal bulb is easy to change, and you might appreciate the increased headlight brightness (the exponent for output is 3.4, so running a 12.8v bulb at 13.8v gives 29% more light). But think of the bulbs that are a PITA to change (dashboard…) and while you're in that neighbourhood, spare a thought for other fragile, voltage-sensitive components like the instrument cluster voltage regulator.
In reasonably mild ambient temperatures, and with a battery in good health, 14.5v is pushing it. You might want to do some deeper digging. Try putting a hot hairdryer on the voltage regulator and watch what (if anything) happens to the line voltage with the engine at a fast voltage. Try the same thing with an upside-down canned-air duster in place of the hairdryer.
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